Blizzard has identified 100,000 World Of Warcraft players guilty of botting, and have banned them for six months.
Blizzard used a sweeping definition of botting, including any form of automated action. This may be the rationale for the game not banning players permanently, as the intention is to get players to behave better.
Clearly, these botters represent a small number of the population, between the 7 million active players, and the 3 million who have dropped off. Blizzard is playing nice not so much because they’re scared of losing players, so much as they just need to take action on cheaters.