Huffington Post launched "badges" today, which means that soon your Facebook friends will all know that you've looked at 20 "cutest baby bump!" slideshows. Niche early adopter/Web nerd favorites like TheSixtyOne and Foursquare have been doing this for a while, but you heard it here first: extrinsic reward systems are mainstream.
I'll put money on the New York Times launching a classed-up badge system by the time their paywall goes up, if anyone wants to take that bet.