The online matchmaking industry turns out to be a great boon for students of human sexuality such as your humble columnist. Don't get us wrong: Our own social life centers on physical venues rather than virtual ones. But dating sites collect large amounts of data about their users, and at least one of them uses that information to produce some interesting amateur social-science work.

Our Valentine's Day survey of sexual social science prompted a reader to send along a 2009 blog post by Christian Rudder of OkCupid.com. The post...