Valve have just added Steam Badges to Steam profiles. How? Using computers! Why? We don't know! They're essentially achievements for using Steam itself - for example, by commenting on your friends' profiles, posting screenshots and recommending games you work towards unlocking the 'Pillar of Community' Steam Badge. Other badges spotted include 'Years of Service' (which levels up with each year you've been a member of Steam), as well as Steam Badges for past events that are now impossible to acquire: 'Steam Holiday Sale 2011', 'The Great Steam Treasure Hunt', 'Steam Summer Camp' and 'The Potato Sack' (which seemingly replaces the Golden Potato item awarded for finding all 36 potatoes in last year's Portal 2 ARG).
Let us know if you've spotted any more. The idea seems to be to promote involvement in things like, oh, off the top of my head, the Steam Summer Sale that's heavily rumoured to be starting this evening. Oh god, I'm excited.