And some metrics aren't just a "game", but are gamed for very real benefit (e.g., gaining admission to a college, getting a promotion, being more employable) in ways that are counterproductive to pretty much all other goals.

So, when something like HN has goals, and you create, say, something akin to a contest and link it to real-world benefits (e.g., people expect a recruiter or hiring to use that "who knows what" info), then many people will modify their behavior, probably to the detriment of original goals.

Why? All my game times are inflated because I either don't shut it down when i go away or I alt tab out of it, do something productive and forget about it :)