They do do checks as I was locked out for half a day a while ago while they checked my activity records (I guess) but the bots are getting more complex, I hear and can be hard to detect. Multi accounting is hard to stop as proxies and other methods can disguise this sort of activity. Really the only way I can think of to restrict multi's is to add restrictions such as account verifications and identity checks at sign-up and that can turn potential customers off before they even try the game in question.

I don't cheat at all by the way so it doesn't matter to me but the last time they did a mass banning the screams and wails could be heard around the world. Unfortunately many of those cheaters just got a free holiday period as food consumption was turned off and they were put into truce. Most of the time the accounts were reopened without problems but every now and then they find a botter or multi and they are dealt with. It's just not as easy to prove cheating as you might think and an honest player can begin to look like a cheat to a relative n00b when they don't know the game well and what is possible.