Hmmm does the grochery store reimburse you for goods that were stolen once they reached your house?
wait... I dont know if that example works well LOL....
Microsoft is responsible to a certain extent. Check the Terms of Service you agreed to upon registering for Live. Theyre at no fault for the theft, damage, financial impact, etc of what happens to your account, outside of the preventive measures theyve set in-place.
Theyre doing everything they can to keep your information safe BUT there are a few things they cannot control. Those being the lengths to which people will try to manipulate their system AND the stupid actions of people who put their account information in jeopardy (i.e phishing, etc).