Airbnb picked nights booked because that is their actual revenue model, and its also their differentiator. A person booking a house/an apartment is more likely to stay for more than 3 days (which is an average hotel stay). Since they also make commission on each night booked, it makes sense to choose this metric. It’s a proxy for how well the consumer trusts the product, and shows a completed transaction in this two-way market. A team could game this metric by offering discounts for extending their stay. Facebook uses 7 friends in 10 days to measure how engaged users are and how much of their social network is actually on the platform. It’s a proxy for how many social networks are there, and density. A way to game it would be to offer the user “people you might know aggressively” based on different parameters, or to sync contacts in some way or another. This might bother a lot of users, since a lot of people ignore those recommendations for a reason, which might have the opposite effect on the platform. Slack uses 2,000 messages to measure if teams are actually using their platform full time, and it’s a proxy for if the team actually considers Slack their main communication space or not. A way to game this would be to count engagement/reactions/bots as messages, but this would make it a weak indicator and a noisier product overall as well for the user. In all of these, if a product is gamified too much for metrics’ sake, it will eventually drop user retention as it will probably be a worse product from the user side, and a weaker indicator of how well the product is actually doing, which uis what Goodhart’s Law states.
