Microsoft Xbox live placed several charges on my bill late last month (September 2010), all on the same day, totalling over $200. I contacted my credit card and been given a temporary credit pending investigation. The representative indicated that she has had several calls like this in the past few days. This card is not registered with Microsoft in any way and has never been used to purchase online.
I just wanted to warn people to carefully check your statements for charges you don't recognize, even from big companies like Microsoft.