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Sometimes I think a kind of virtual presence on the web would be nice. Not like the IM Available/Away/Busy thing, but more like, if I happen to be looking up the lyrics to some song, I can see who else is looking and strike up a conversation or just virtually "wave".
You'd need opt-in from browsers and websites to make it work though without it being a total privacy nightmare. I was thinking of complicated encryption scheme to support this...but, notionally, it's like if every web page had a little chat room associated with it that you could optionally join when you visit the page, but not at other times.