They may ask where you got your money from but that's usually it and a vague answer is enough like "it was used for payment of services in 2012" or "I've been day-trading for the past two years on so-and-so exchange". As long as there's nothing fishy about your answer, they'll do business with you. If/when law enforcement comes asking, they'll provide your answer about source of funds. If you lied to them, THEN you get in trouble with law enforcement.
I already had a such talk with them before. And after that I got such situation. This is most strange stuff, we got the deal, and now they are closing my account.
In any way, they don't have right to take out my own money. Its not in their rules. If so, then this bitstamp is not trust worthly at all. And I will not leave it like it is, will make hype as only I can.
Making a business? Do it fair.