Airbnb chose nights booked because it showed how many people were actually using the app to find a place to stay. I think this makes sense because the more nights people book, the more useful Airbnb seems to be. However, if Airbnb only cared about increasing this number, they might focus on getting more bookings instead of making sure customers have a good experience. This could lead to unhappy customers.
Facebook noticed that people who added seven friends within their first ten days were more likely to keep using the app. I think they chose this because people are more interested in Facebook when they have friends to interact with. However, if Facebook pushed people to add friends just to reach that number, users might start adding random people they don’t even know. This would increase the number of connections but wouldn’t make the app more enjoyable.
Slack used 2,000 messages because it showed that teams were starting to use the app regularly to communicate. I think this was a good way to see whether teams found Slack helpful. However, if Slack only wanted teams to send more messages, people might start sending unnecessary messages just to reach that number. This could make the app distracting instead of helpful.
What I learned from these examples is that having a goal based on numbers can be useful, but it doesn’t always show the full picture. This connects to Goodhart’s Law because once companies focus too much on reaching a number, they might forget what actually makes their product useful.
Sources:
“8 Timeless Analytics Resources.” Amplitude, 2016, https://amplitude.com/blog/8-analytics-resources.
“Goodhart’s Law.” Wikipedia, Wikimedia Foundation, https://en.wikipedia.org/wiki/Goodhart%27s_law. Accessed 27 Oct. 2026.
Rachitsky, Lenny. “Choosing Your North Star Metric.” Future, 2021, https://future.com/north-star-metrics/.
“Slack’s Founder on How They Became a $1 Billion Company in Two Years.” Fast Company, 2015, https://www.fastcompany.com/3041905/slacks-founder-on-how-they-became-a-1-billion-company-in-two-years.
