Why did each pick that number?
All three companies identified the earliest observable event that predicted lasting value. Airbnb needed a metric that predicted both sides of its marketplace and revenue, which booked nights does. Facebook compared retained and churned users and found that people reaching 7 friends in 10 days rarely left. Slack found that 93% of teams that exchanged 2,000 messages continued using.
What behavior was it a proxy for?
Insiders said the numbers were somewhat arbitrary, but gave their team a clear goal, and were proxies for experiences. Airbnb’s nights booked stood for trust between strangers becoming a completed stay. Facebook’s seven friends meant a feed worth opening, since no friends meant nothing to read. Slack’s 2,000 messages stood for a group moving its communication habits to Slack.
How could a team game it?
Airbnb could subsidize stays with discounts or loosen listing standards. Facebook could flood new users with weak-tie friend suggestions. Slack could enable auto-posting and onboarding prompts that generate filler messages.
What would that do to the product?
Gaming would undermine the experience the metric was meant to signal. Airbnb would get more nights but worse stays. Facebook users would reach seven friends but not care about their feed. Slack would fill with noise and people would start muting channels or switch platforms.
Seeing how easy it is to game the metrics highlights the importance of pairing metrics with guardrails that measure value, such as repeat bookings for Airbnb or engagement with friends’ posts for Facebook.
Sources
https://www.sec.gov/Archives/edgar/data/1559720/000119312520294801/d81668ds1.htm
https://review.firstround.com/from-0-to-1b-slacks-founder-shares-their-epic-launch-strategy/
