At least to some extent, dating sites have made the opposite. The more people know about each other, the greater the variance in their assessments of each others' attractiveness. ISTR a study that showed that the less people know each other before starting dating, the more likely people are to end up with partners who are about as physically attractive as themselves.
This is a good point. I guess it's important to remember that dating sites do actually change people's behaviour, rather than being a representation of how everyone behaves.
