I'll add to the definition, "A meme is a viral idea with an unpredictable life of its own."

The phenom of LOLCats started out as a meme on 4chan.org, one of wild west frontiers of the internet. That little bit of amusement (putting strange captions on cat photos) morphed into the "Cheezburger Network" of blogs and photo-memes. A very profitable business that probably appalls the old hands on
4chan

This is one of the funniest cartoons I've ever seen, period. It sums up the smarmy charm of 4chan.org and has a nice writerly bent as well.