I got a surprise in my email this afternoon - an FYI message from my GM World Mastercard account, confirming the successful change of the email address on my account. The surprise was that I hadn't made any change, and the new address wasn't mine. I quickly went online and changed it back, verified that no new charges had been made, then called the customer service number and reported the incident. They cancelled the account and they're issuing me a new one, but it really annoys me that someone managed to get into my account and change it without much trouble. The customer service rep said there was no log of the change, but that they only log change requests when they're done by phone, so it must have been changed over the internet.