Airbnb: Nights booked
Facebook’s early growth team: 7 friends in 10 days
Facebook’s early north star works because it’s a threshold they found where new users become far more likely to stay on the app. It proxies network density and feed quality. With more friends, the feed becomes more interesting to the user because of social reasons. To game it, Facebook could push aggressive “People You May Know” prompts and contact lists to inflate connections, or set up auto-request flows when a user onboards, or count low-quality connections such as strangers or bots. This would produce a feed that is less interesting for the user, producing spam and privacy problems.
Slack: teams that sent 2,000 messages
Slack’s north star is from a finding that teams that crossed roughly 2000 messages almost always stuck around (93% retention). It proxies team-wide habit, because once usage crosses that threshold, it means people of that team are using it in replacement of other forms of communication such as email or text. Organizational history also lives there, so it signals dependency. To game it, one could count bot messages, prompt users to say “hi,” and streaks. This would make Slack noisier and contribute to notification fatigue while usefulness falls.
