Anonymous is my biggest one.
The idea of "hacktivist" and "doing it for the lulz" or "I'm doing this for freedum!" is just so absurd I cheer a little when some of those nuts get caught and put in jail for the stuff they've done. Then the ones who don't actually do anything but think Anonymous is their god make me cringe.
It's probably one of the biggest fads out there currently, and the world would be a nicer place with that junk not cropping up everywhere.