This was a post about a ban wave that happened about a week ago, and the blue response.

There's some really interesting sociological hocus pocus behind it, but from what I understand, the TLDR is that if a botter gets permabanned, they'll often just buy a new account and go right back to botting. However, if we only suspend them -- meaning, they'll get their account back later -- they're less likely to buy a new one. Furthermore, once they do get their account back, they're EXTREMELY unlikely to bot again.
Seems like they're working on stopping the casual players who may have been tempted to try out a bot. I doubt that will do much against the professional bot, who will both create a new account and be able to use the old one again in 6 months.

http://us.battle.net/wow/en/forum/to...6375?page=2#24