My wife and I don't use sex to barter, but we do bet with sexual favors. For instance, she'll say, "What chick movie was that guy from Gray's Anatomy recently in?" I say Sweet Home Alabama, she says My Best Friend's Wedding. I'll say, "Anal sex if I'm right." She'll say, "No sex-just cuddling and talking if I'm right."

We always do it in fun, and never for stakes the other wouldn't object to doing- too terribly anyway.