Lenny’s Podcast: Product | Career | Growth

Episode: Slack founder: Mental models for building products people love

Guest: Stewart Butterfield (Founder, Slack & Flickr)

Date: November 20, 2025
Host: Lenny Rachitsky

Episode Overview

In this special episode, Lenny hosts Stewart Butterfield, the renowned founder of Slack and Flickr, for a rare deep-dive into his philosophy and mental models for building products people love. Stewart shares lessons on product utility curves, product taste, the importance of continual improvement (including embracing embarrassment), the value of "delight" and craftsmanship, the nuanced understanding of product friction, organizational pitfalls (Parkinson’s Law and “hyperrealistic work-like activities”), reflections on pivoting, and his ethics of generosity in both company building and customer relations.

Key Topics & Insights

1. What Stewart Butterfield Has Been Doing Post-Slack

[05:28]

• Stewart has spent the past 2.5 years since leaving Salesforce enjoying family time and working on philanthropic and creative projects.
• He frequently brainstorms new ideas with Cal Henderson (Slack’s CTO), but is wary of contributing to current tech addiction problems:

  “If you could find some way to make software that helped people use their phones less often, that would be a big winner.” [05:55]

• No new company in the pipeline but plenty of support for other artists and philanthropic work.

2. Utility Curves: The S-Curve of Product Value

[06:44], [07:07]

• Stewart popularized “utility curves” within his teams — the S-shaped curve that helps judge where effort yields significant value.
• Early investment in a feature can yield little, but there’s a critical “aha” zone where it becomes indispensable. After that, improvements yield diminishing returns.
• Applied to everything from hammers (“junk, junk, junk… okay, good, great”) to software features.
• Critical for resource prioritization. Many features fail not because the idea is bad, but because it wasn’t invested in enough to cross the “value threshold.”
  • Quote:

    "We would try to really investigate and decide whether we were on the first shallow part of the curve, the second shallow part, or just coming up to it." [09:20]

• Continual movement of standards (drawing on Bezos’ "divine discontent") means the goalpost of delight keeps shifting as products mature.

3. Craftsmanship, Taste, & “Tilting Your Umbrella”

[15:11]

• Slack stood out by obsessing over “delight,” borrowing cues from consumer UX for a B2B product.
• Stewart believes “taste,” like cooking, can be developed but is rare in product leadership.
  • Quote:

    “Most people don’t have good taste and don’t invest… Your failure to be truly empathetic is an advantage you can create, a critical advantage.” [19:03]

• "Tilting your umbrella" became Slack’s internal metaphor for product empathy: noticing and addressing small irritations others ignore.
  • Story: In Vancouver rain, only 1/3 of people would tilt their umbrella to avoid poking others; Slack cultivated the attitude of caring about these “small” impacts.

Slack’s Delight & Craft Choices

[20:37]

• Magic links: Pioneered passwordless email login for convenience.
• Notification defaults: Opted for “all messages” notifications until users hit a threshold, then educated them about better settings.
• “Shouty Rooster”: When users typed @everyone, a visual warning would appear, discouraging overuse (helping shape organizational communication etiquette).
• Do Not Disturb: Balanced rollout considering both administrators and end-users, default timings, and override options for real user empowerment.

4. The Right Kind of Friction & The Peril of Over-Optimizing For Clicks

[28:46]

• Stewart’s controversial take: friction is often misunderstood. Reducing “steps” isn’t always the goal; clarity and comprehension matter more.
  • Example: For core flows (e-commerce checkout), friction REALLY matters. For onboarding complex tools (like Slack), helping users understand is even more critical.
• Comprehension is the main challenge for new features, not mechanical “friction.”
  • Quote:

    “Don’t make me think… If your software kind of stops me and asks me to make a decision and I don’t really understand it, you make me feel stupid.” [37:04]

• Menu design: Don’t minimize clicks, maximize clarity. If users face too many options at once, they’ll get overwhelmed and confused.
• Anecdote: Observing teens using Snapchat showed that rapid, easy, thoughtless actions were crucial—don’t inhibit fluidity with artificial “simplicity.”

5. Relentless Dissatisfaction and Continual Improvement

[45:06], [49:10]

• Stewart embraces embarrassment as fuel for improvement:
  • Quote:

    “I feel like what we have right now is just a giant piece of shit… we should be humiliated we offer this to the public. Not everyone finds that motivational, though.” [00:00], [45:52]

• At Slack, posted quotes about always seeing “limitless opportunities to improve.”
• Teams at Stripe and elsewhere (e.g., Patrick Collison) exhibit a similar restlessness; the best product leaders are never satisfied.

6. Parkinson’s Law & Hyperrealistic Work-Like Activities

[54:30], [57:11]

• Parkinson’s Law: “Work expands to fill the time available for its completion.”
  • Observed especially as organizations grow: every manager wants to grow their team, not out of malice but ambition/career logic.
• Anecdote: A minor UI change (auto-inserting “@” in threads) generated hundreds of hours of process, meetings, and analysis—cost far outweighed benefit.
• “Hyperrealistic work-like activities”: Meetings and projects that look like “work” but create minimal value. As orgs mature, these become pervasive.
  • Quote:

    “…if you hire 17 product marketers, you’re going to have 17 product marketers’ worth of demand for work to do. And if you don’t have sufficient supply of product marketing work to do, they’re just going to do other stuff.” [62:35]

• The solution: Leaders must curate and clarify “known valuable work” or teams will gravitate to unproductive busyness.

7. Legendary Memo: “We Don’t Sell Saddles Here”

[68:32]

• Written as an internal Slack memo (before launch) to anchor the culture on communicating REAL user outcomes, not features.
  • Quote:

    “It’s not enough just to build a great product. You have to put effort into communicating what this does for them, the problem this is solving for them, the outcome this is going to achieve for them.” [70:11]

• Metaphor: Don’t market the saddle; market the excitement/adventure of horseback riding.
• Startups need to create both product AND market understanding, which often means synthesizing existing concepts in new combinations (“Uber for __”).

8. Pivots: When & How to Move On

[73:20]

• Stewart has pivoted twice (Flickr, Slack), both from failed game ideas.
• Perseverance is over-glorified; “hang in there” isn’t always right. The correct time to pivot is after exhausting every non-ridiculous path.
  • Quote:

    “You have to really be coldly rational… because it’s fucking humiliating.” [75:38]

• Pivoting is emotionally hard: you risk humiliation after persuading employees/investors of the original vision. Distance yourself enough to decide intellectually.
• Compare Melanie Perkins (Canva) perseverance: sometimes the answer is NOT to pivot, but to keep refining your case.

9. Generosity as Company Ethos & Competitive Advantage

[78:30]

• Stewart’s generosity (to employees and customers) is a recurring theme—examples cited: paying severance, covering 100% health insurance, fairest possible billing and outage credits, and making sure employees benefited from Slack’s success.
• Not just altruism: iterated generosity encourages future cooperation (Prisoner’s Dilemma). It also attracts ethical employees and aligns with the long-run success metric:
  • Quote:

    “In the long run, the measure of our success will be the amount of value that we create for customers.” [29:00], [85:22]

• Designed refund policies to be proactively credited, even if service interruptions didn’t affect a specific customer:

  “We will automatically… apply this credit to your account and just send you a message… even if the issue didn’t affect you as a customer.” [84:52]

10. The “Owner’s Delusion”

[86:38]

• Coined by Stewart from a Twitter exchange about terrible restaurant websites: business owners design for themselves, not their users' real needs.
  • Example: Restaurant sites with music, animations, no clickable phone/address, missing what users actually want.
  • Quote:

    “Take a breath, pretend you’re a regular person, and then look at this again and see if it makes sense…” [89:31]

• The challenge: Recognize and actively combat the delusion that users care as much as you do.

Notable Quotes & Memorable Moments

• “I feel like what we have right now is just a giant piece of shit…you should be embarrassed. If you can’t see almost limitless opportunities to improve, then you shouldn’t be designing the product.” – Stewart [00:00]
• “Don’t make me think.” – Stewart [37:04]
• “Tilting your umbrella is our opportunity…your failure to be considerate…is an advantage you can create.” – Stewart [19:03]
• “If the problem seems simple, you don’t get it.” – Stewart [57:12]
• “In the long run, the measure of our success will be the amount of value we create for customers.” – Stewart [29:00], [85:22]
• “Hyperrealistic work like activities is superficially identical to work…” – Stewart [62:35]
• “It should be a perpetual desire to improve. You should never be like, oh, this is great.” – Stewart [45:52]
• “If you don’t name it and recognize it and discuss it and…pretend you’re a regular person…you’re screwed.” – Stewart [89:31]

Timestamps for Important Segments

• 05:28 — What Stewart is doing post-Slack
• 06:44 & 07:07 — Utility curves and the S-curve for product value
• 15:11 — Taste, empathy, and the “tilt your umbrella” metaphor
• 20:37 — Examples of delight: magic links, notification defaults, “shouty rooster”
• 28:46 — The value (and risk) of product friction
• 37:04 — “Don’t make me think” and the cost of cognitive load
• 45:06 & 49:10 — Relentless dissatisfaction and improvement
• 54:30 & 57:11 — Parkinson’s Law, organizational pitfalls, and hyperrealistic work
• 68:32 — The “We Don’t Sell Saddles Here” memo and marketing outcomes, not features
• 73:20 — How and when to pivot (and why it hurts)
• 78:30 — Generosity: with employees, with customers, as an ethos
• 86:38 — The Owner’s Delusion: why businesses miss what users want

Conclusion

This episode is an essential listen (or read) for product builders, founders, and anyone seeking to create better user experiences—or run better companies. Stewart Butterfield combines product wisdom with humility, user empathy, and organizational pragmatism, challenging conventional wisdom at every turn. His legendary product intuition is grounded in relentless self-critique and an unwavering focus on delivering real value for customers.

Host’s closing recap:

“Incredible. I’m just trying to picture the entire team at Slack…hundreds of people chanting that mantra.” [85:28]

Guest’s parting words:

“Take a breath, pretend you’re a regular person, and then look at this again and see if it makes sense…” [89:31]

Recommended further reading:

• “We Don’t Sell Saddles Here” by Stewart Butterfield (Medium)
• “Positioning” by Jack Trout and Al Ries