Yesterday dozens of sites where contacted by blizzard legal and given the option that many have faced. Stop selling bots or they will attempt to sue you in court. This first happened when mmoglider formally known as wowglider was contacted by blizzard.
They basically told him to shut down mmoglider or they would take him to court. The case went to court, glider lost, and blizzard settled out of court to finish the case.
Blizzard has been known to go around to different private server and botting sites and give them 2 options. Either take down the material they want, or face an onslaught of legal fees. SO far only 2 people have said no to this. The first was mmoglider which ultimately lost, and the second is honor buddy which is based on Europe and currently fighting the case. It has been thought that since Euro laws favor the defendant more that they will prevail, but that case is months in the future.
The sites as of yesterday that have shut down so far have been the other major bot makers out there.
Pirox - Famous for his fishing bot, and level bot. The site does not accept any new joins right now and will fully shut down in january 2012.
Crawlerbots - Famous for another free working fishing bot and a paid leveling bot. They have shut down completely.
lazybot - A famous world of warcraft leveling bot.
We are sure other sites have shut down and as we find out we will update them.
Sources -
PiroxCrawler BotsMMO Lazy Bot