Just thought of the idea of integrating achievements. If you've played Call of Duty: Modern Warefare 2, you earned achievements (which unlocked avatars to use) for accomplishing certain things. If you've ever played Neopets, I believe they have Trophies.
But basically you can earn badges/achievements/trophies (whatever they should be called) doing certain things. For example: reach a score of "500" on <insert game name here>; lose 20 times in a row on <insert game name here>; etc.. Random stuff, and not so random stuff.
Then players can socialize and ask each other how they got that badge/achievement/trophy. Or players might play a certain game in ways it wasn't made to be played in hopes of unlocking a yet to be discovered achievement.