From what I've read, if you're a big client (re: you make them a lot of money) they'll work with you to solve the problem. But if you're a peon like the rest of us, you have to inform them if you suspect such activity, or else they'll assume you're in cahoots with the criminals, and take it out on you (re: ban your account). So if you suspect this is happening to you, email them right away and inform them of your suspicions.