Since I know there are a lot of OKCupid users here in GT Space, here's Ars Technica writer John Timmer on a study regarding how users of the service interact based on race.
The article starts by pointing out that in most cases, Americans prefer alters, or potential partners, of the same race. And so:
Using massive amounts of data from the dating site OkCupid, UC San Diego's Kevin Lewis looked at how this self segregation plays out in the online world. Among all of the ethnic groups he examined, there's a strong tendency for people to send messages to other users who belong to the same ethnic group. But people who are willing to go against that trend are typically rewarded—recipients of those messages are more likely to respond to them. And for a short time afterward, they're more likely to initiate contacts across racial boundaries.
The limits of the study were for straight single people looking to date, and only sampled about 125,000. But of those 125k,
... 48,000 users were the recipients of messages from someone outside their racial group. Lewis then tracked the users' behavior over the weeks following that message and found that it briefly changed their behavior. For a few weeks afterward, these users were 37 percent more likely to initiate contact with someone outside their own group. Thus, simply getting a message from outside your ethnicity seems to open your thought process to other possibilities, at least for a little while.
Lewis speculates further that after awhile the number of messages from users of alternate race potentials gets drowned out by those of the same race. But for a short time, brief contact with people from another race seems to make individuals behave in a more open minded manner (note, I'm not saying they're necessarily more open minded).
Note, the Ars article does confuse race and ethnicity very briefly but I don't think in any problematic way.
A commenter to that article points out this older 2009 article by OKC themselves which analyzed race data that gives some context for how race relations tend to break down across all sorts of statistics, including preference declarations and response rates. Prior warning, though the charts and graphs it supplies are pretty, the overall message isn't.
Curious how those GTers who have used OKCupid or are using OKCupid feel about it. Certainly in many cases the people someone meets in their own social circles might be limited, whereas Internet dating suddenly opens up your identity to whole new pools of people that you would never have considered.