Facebook’s 7 Friends in 10 Days: Facebookâs early growth team found that users who hit this milestone rarely stopped using the service. It was a perfect proxy for the crucial moment of experiencing a populated, engaging news feed.
- Gaming it: A product team could optimize this by automatically adding suggested contacts or aggressively scraping user address books without friction.
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The Result (Goodhart’s Law): Feeds would fill with strangers and spam. The core value of genuine connection would break, causing long-term engagement to plummet even as the initial metric spiked.
Slack’s 2,000 Messages Sent: Slack realized that once a team sent 2,000 messages, they had integrated the tool into their workflow and were highly likely to pay. It was a proxy for lock-in and daily habit.
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Gaming it: Teams could push automated bot integrations or system alerts (like GitHub pings) to artificially inflate message counts.
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The Result: Channels would become instantly noisy and unreadable, prompting users to mute notifications and ultimately abandon the tool entirely.
Airbnb’s Nights Booked: Airbnb chose this to represent the dual-sided value of their marketplace: a host successfully gets paid, and a guest gets a place to stay.
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Gaming it: The platform could heavily incentivize dirt-cheap, low-quality listings or ignore fake bookings just to pad the aggregate numbers.
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The Result: The platform floods with scams or terrible properties, completely destroying guest trust and brand reputation.
The law notes that if a measure becomes a target, it ceases to be a good measure. In other words, if you only optimize for a single number, you will eventually destroy the product that gave that number value in the first place.
