I know a lot of people who've met their boy/girl friends online. I first talked to my boy online... but we lived in the same town so then happened to bump into each other or whatever.
I think sometimes it's a good way of getting to know people with similar interests, etc who you might not otherwise ever meet, but I don't think I'd ever use websites specifically designed for online dating... I think it's a little weird/presumptuous, although I can see that maybe if you're older you wouldn't happen to be using other profile sites/orums/whatever else.
I think it's an option, not a bad one or a good one. I mean, meeting the love of your life through a federal prison pen-pal system is quite less savory, I think