Blizzard's had all it can stands, and it can stands no more. The studio is taking aggressive action against botters and cheaters in Diablo III, reporting that it's gone through "several rounds of account bans" against such players.
The studio also used the ban announcement as an excuse to clarify its position on hacks and third-party software. If you're curious about what steps over the line that Blizzard has in mind, wonder no longer. Beyond allowing some players to get away with an unfair advantage over others, cheat programs reportedly cause instability and performance issues with client software and Battle.net at large.
"We strongly recommend that you avoid using any third-party software which interacts with Diablo III," Blizzard posted, "even if you are accessing that software from a reputable third-party site-as doing so can result in permanent ban from the game."