What websites do you use where you earn points, awards, stickers, badges, etc...?

Excluding the obvious (Fluther), what websites have you joined where you can earn stuff for being an active user? What do you specifically earn and how? Is it addicting? Does it make you invest more into the site? What do you get out of it? How long have you been a member? Which one is your favorite?

If the website were the same but didn’t award you anything, would you still be as active on it?