Really, consider the fact that what is going on here is nothing more than the same gossip from before, but now in electronic format.
People talk, people gossip, people are social creatures, and as it often appears to be, people are cruel. Just because someone wrote a comment about you on some internet 'bathroom wall' or even a real bathroom wall doesn't mean you have to do anything about it, or even recognize it. In both cases, the anonymity of the posting is its very downfall. On the other hand, if you have people outright spreading gossip and clearly linking it back to themselves (the real-world equivalent of saying "yeah, I wrote that"), then the problem is more pronounced, but still the same as before. You can deal with gossip if you know who starts it, or you can deal with gossip by ignoring it.
If colleges can't teach to their students that gossip is best ignored, then we have more things to worry about than the gossip itself.