Not surprised.
Some hackers do it because they have nothing else to do (pathetic, but hey, it happens), some do it because they're paid to do it, some do it because it makes them feel special. I mean it won't stop tomorrow or anytime soon, Diablo III will be hacked, although I guess it will be very difficult to do so, but not impossible.
That's why it shouldn't require on-line connectivity to play it, for those who would prefer to play it entirely off-line without having to deal with hacks and bots. I hope that at the very least we'll be able to password our own created game and that we'll be able to play alone even if we're on-line, that would be the bare minimum.