It actually depends on which game you are talking about, but it's true that the majority of MMO makers are very anti-bot. Undoubtedly, Blizzard is not having an

It actually depends on which game you are talking about, but it's true that the majority of MMO makers are very anti-bot. Undoubtedly, Blizzard is not having an issue with botting itself, they are having an issue with a tool which can be used for gold farming (see: Bittorrent). The various forms of fraud that gold farming shops use to get accounts (such as credit card fraud) result in non-trivial amounts of chargebacks; I can't name figures, but MMO companies lose enough money from fraudulent players, namely farmers, that combating them justifies the hiring of full-time fraud specialists. Players, and probably moreso, game designers are also interested in combating farmers in order to maintain the 'purity' of their in-game economy. I guess what I'm basically saying is that gold farming is the real enemy in this battle. Players and designers could also be bothered that bots allow players to make progress in the game without actually having to put in the time to play, but this plays second fiddle to gold farming.