So, I get an e-mail today that someone tried to buy the $70 xbox live point pack. I don't leave an active card with my xbox live account, so I got an e-mail from xbox live saying they couldn't charge me. All of my current xbox live points were gone though.
I did some research and noticed that a LOT of users are experiencing this same issue, and all of them have Fifa 12 achievements showing up. I do not own, nor have played Fifa 12, but this seems to be a common link. It appears that something is going on with xbox live that is a serious flaw allowing others to access accounts. I will be opening a case to get my points refunded, but Microsoft needs to look into this.
For the record, my password is both unique and strong, nor do I share it.