I can't speak to legality of the researcher's actions, but as a Social Scientist (cue jokes about not being a real scientist), I can tell you that their actions were unethical. Specifically, I'm shocked that their Internal Review Board (IRB) thought it was ok to upload this data to a forum where all can have access.
Social Scientists, when conducting research, are under a moral obligation to make sure that their participants are not under more than 'minimal risk' as a result of the research. The most common heuristic for that minimal risk is whether the researchers are making the participants susceptible to more risk than they would normally be susceptible to. In this case, while the participants had provided data to a semi-public forum (i.e. OkCupid), make the data more easy to extract and able to be mined is definitely putting the participants at higher risk for data related crimes (e.g., identity theft, bank fraud).
If those researchers aren't in proverbial hot water yet with their institutions, they will be when the law suits come. The lesson to be learned here if you are a researcher....your IRB exists for a reason; check with them before creating a new protocol.