I don't remember if I ever actually posted in this thread...maybe I did, maybe I just meant to and kept forgetting.
Anyways, although the discussion has moved way beyond the subject by now, I thought I'd just share my experiences. I guess just add it to the large pile of anecdotal evidence that okcupid can work.
Many years ago I signed up for okcupid and within a very short period of time, met someone to just have casual sex with. A few weeks later it happened again. Then I met a girl who I dated for several months. All of this within a short period of time. I shut my account off when I started a serious relationship with someone I didn't meet on okcupid. But opened it up again a few months ago and within a week had several date offers and one offer of no strings attached sex. I ended up closing the account again before I could do anything with those offers though. I had other priorities at the time.
So basically, it works. Give it a try. I didn't initiate a single contact the whole time, just let girls message me first, and I still got plenty of messages sent to me and had some real world successes. That said, my friend uses okcupid and aggressively sends multiple messages every week to at least a dozen different girls and ends up with far more interested parties than I do. So if you really want it to work, it's probably best not to be a lazy fuck like me who just relies on being decent looking to get interest.