Here's a quote from the Diablo group on facebook I came across:
"Blizzard Entertainment has always taken cheating in any form in Blizzard games very seriously, and that's no different for Diablo® III. If a Diablo III player is found to be cheating or using hacks, bots, or modifications in any form, then as outlined in the Diablo III end user license agreement, that player can be permanently banned from the game."
Excuse me? "Blizzard Entertainment has ALWAYS taken cheating in any form in Blizzard games very seriously" ALWAYS!? No, only recently, only in WoW and Diablo 3, possibly in Warcraft 3 I didn't play that online.
Since the beginning of Diablo 1 it was chock full of cheaters and hackers. There was a duplication bug in Diablo 1 that NEVER got fixed except in a patch in the Hellfire expansion which was made by SIERRA, not Blizzard. There were hacks that changed the game in weird and messed up ways. There was a hack that made all the cows do the dialogue for people and the people do dialogue for cows. There was a hack that made every single free space in town a pile of 5,000 gold. There were too many hacks to count, and there were many programs out there just dedicated to these types of hacks.
Diablo 2 was also chock full of cheaters and hackers. And now, all Diablo 2 is if you make a multiplayer game is a bunch of spam bots joining and being douches so you can't even make a game of that anymore it's so bad. Well I guess that's still better than what it used to be...create a new game for a lowbie character and even with LEVEL RESTRICTIONS max levels join, make the game harder and just stand outside the Rogue Encampment herp derping it about doing nothing. And to join a game with level restrictions in place, they must be hacking it. Also the amount of character editors for Diablo 2 was pretty much as numerous as the hacker trainer programs that existed for the first Diablo.
Warcraft 2 was full of map hackers and other types of hackers. Hell, some maps even the basics were hacked like terrain, there were maps where they managed to change what terrain was what, making trees normal ground!?
Other games I'm not sure of as I didn't play them online, but with all this they cannot say that they've ALWAYS taken cheating very seriously. They may take it seriously in Diablo 3, but that's pretty much because your character is stored on their server, in order to hack your character you have to hack their server somehow. That's a major security breech and other companies have been suffering from. Blizzard just doesn't want to look weak like Sony and various other companies.