I do have a profile up at OKCupid for fun just as a social experiment. Written commmunication is a different medium from face-to-face, so a lot of what I leaned is probably just specific to on-line, but I did learn a few general points applicable to dating in any setting:

(1) Direct sexual come-ons are generally disasterous.

(2) Unless you are very attractive, you are going to have a hard time getting action from strangers, looks matter a LOT more than people are willing to admit, and that's true for both men AND women.

(3) The very hint of a formal romantic setting or 'date' immediately puts people on the defensive and stops them having fun - kinda sad. The same girl that would chat to you quite happily in a non-dating setting will suddenly clam-up and stop giving you the time of day in a dating context. Weird but truth.

If you are a guy, I wouldn't recommend dating websites unless you think you are in the top 20% in the looks department and can handle a lot of rejection. Generally guys only get a response rate of 10-30%, and its near impossible to keep a girl talking to you for any length of time, since they are constantly being bombarded by messages from hundreds of other guys.

In short, these places are definitely not good places to meet people. I got far more action on wotmania in a week than I ever did in a year on OKCupid