Well, I joined one about 4 years ago, sent messages to about 10 girls, heard back from 3 of them, went out with 2 of those, and the later I've been dating for the last 3 1/2 years.

She turned out to be far cooler than anyone in my "real" life social network, by far. I was only on the site for about 2 weeks. Best $10 I ever spent.