Getting a web design class to play OP2 is not that bad, you'd expect it to not be populated by your average idiots.
Social networking sites? You expect them to be filled by your average, and worse, idiots.
And yes, check post dates.
We have a problem with poll topics, in that whenever someone casts a vote, the topic registers it as a new post, even if it had been dead for years. Take extra care with those.
Also, if you can get an admin to check it, there should be an option if you're using the forum software I think you are.
Admin CP > [Forum Control] Manage Forums > Settings (of each individual forum...), then down on the bottom it should say "Allow votes to bump a topic? Yes No "
I'm guessing you guys have Yes checked on every forum. Then again, that's IF. I dunno if you guys are using IF software or not.