Yeah, it's not as if MS wasn't paying back the customer's losses or anything,,, oh... wait... they are.
For the customer, this is an annoyance, they have to lodge a claim, be put out a bit by not having access to their account, and not have access to some funds for a while, until they get refunded.
For microsoft, this is a very real loss, of money, resources, and goodwill. Do you really think that if there was an easy solution, they wouldn't be looking into it?
Honestly, when I consider the effectively year long timeframe that this fraud has been occurring, I think Microsoft has had a breakdown in the feedback loop from End Users -> Customer Service -> Developers. It seems like CS has been handling this issue, but the problems haven't fed back to XBL development teams such that they can work on countermeasures. By any standard, 9 months is just too long to be handling this on a case by case basis without any response from the development team.