I think the problem with dating sites at the moment is that they make it easy to lie. If you've ever used Match.com, or something similar, the dates tend to end up poorly because one person who claimed to be into music listens to the radio on the way to work, while the other person who claims to be into music has a Masters from the Royal Academy of Music, has played in professional symphonies and spends eight hours a day practicing. Also, that is NOT and athletic build.
Now, if you monitoring their streams (Facebook, Twitter, MySpace, whatever), you could determine what they liked, where they went and who they knew. I suspect this is way better way to form meaningful connections (it's how I found the love of my life). And if you're just looking for a random hookup there's always craigslist.
I've been looking for a co-founder for the Y Combintor summer 2010 session - http://ineedacofounder.wordpress.com - so if you're interested hit me back and maybe we could team up.