Given that they measure "success" by response rate I'm not sure I put a whole lot of faith in the below quoted analyses. Perhaps the low "success" rate is because people reply w/ an outside service that OkCupid can't track?

"#4 – Don’t try to take it outside. Obviously, all successful OkCupid relationships outgrow our in-site messaging feature. But an offer to chat or of an email address right off the bat is a sure turn off. One of the things online dating has going for it is its relative anonymity, and if you start chipping away at that too early, you’ll scare the other person off."