I dont know if everyone out in the Borderlands Wiki community knows about the bug that is causing player character files to be permanently deleted. if not im just here to warn you about it, i wouldn't want to lose a character i've spent 100+ hours on so i don't want you guys to either.
It's basically where if you join an online game where someone has hacked to gain an ultra hardcore mode then they are infected with a bug. Then if you join a game with the bugged player you will in-turn, without knowing contract the bug and the next time your player dies your character will be forever,Permanently deleted.
For more info on this killer bug go to this BBC article Badass bug killing Borderlands 2 characters its so widespread the BBC is covering it.
SO SOME ADVICE, DON'T GO ONLINE WITH STRANGERS WHO MIGHT BE INFECTED !!