I'd guess its an experiment about when people stop clicking. Most people either only click a few times, or stop right at 20 times, when they receive the easter egg buttons.
So, the lesson is: give your users a perceived reward for taking action on your site, to get them engaged long enough to get the reward.
Or maybe the lesson is: as soon as users perceive there are no rewards left they'll leave.
So, the lesson is: give your users a perceived reward for taking action on your site, to get them engaged long enough to get the reward.
Or maybe the lesson is: as soon as users perceive there are no rewards left they'll leave.