It's a lot like real life. The most obvious metaphor that everyone picks up is the comparison of a meme to a virus. If a meme suddenly gets onto a popular blog--then like a prolific Casanova--the meme starts spreading to all the other blogs downstream.
Actually, I was thinking about the phenomenon of tagging. That is, at the end of a meme, the blogger adds a list of other bloggers they would like to see doing the meme. In this case, the spread of a meme is limited to a blogger's own little clique. Sort of like inbreeding, I suppose. And if a blogger is outside of a certain clique, they're never going to get tagged.
That's probably why I don't do a lot of memes I come across. Sure, I sometimes find interesting memes that I would really like to do. But if it's a tagging sort of meme and no one has tagged me (which is almost never), I figure it's too impolite to horn in uninvited.
