"The real poster child of web 2.0 is tagging. Every website supports it and tags now present a real alternative to traditional search. Tags and the keyword dictionarys that they create provide a domain-specific grammar that can be applied on a hyper-local level, to a specific website. For passive games, tagging doesn?t really apply. However, if we think of tagging as a way for users to express themselves online, then passive games have their own popular form of self expression, that of avatar customisation. Where tags give every user a way of personalising a website (which, in terms of growing up, proves that we?re at The Age of Point at Things), avatars give players a way of differentiating themselves from every other player in the game."

--Duncan Gough, writing on Suttree on about "Casual Games and Social Software"--and there's lots of great thinking here.