The Microgaming/Prima sites have been my bogeyman (Royal Vegas/Gaming Club/7 Sultans etc), always seems to be that one lucky maniac waiting to ambush me.
As for tournament bad beats, how about getting knocked out of an O8 tourney in 20th place to a pair of 3s (no low)? Probably not the smartest call by me, but at that point it was either run with the good draw for a shot at the big money, or fold and pray to hold on for 10th and get my buyin back.