Discovercard whoops....

This isn't tech related except for the mail merge side of things. We got a letter in the mail day before yesterday from Discovercard. It had my name and address on the outside just as it's on record with Discover and everything looked like a normal "account information notice" (read.... ad for some of our services) mailing. When opened up.... The name and address on the letter inside were different (in our town, but someone else/different road/etc.) And the last four digits of the acocunt number were listed. All in all, it could be a much worse data leak, but still.... it's annoying to see Discovercard go and botch a mailmerge like this. (I guess this is why they use "Windowed" envelopes for their bills...) In the past I've had communications from credit card companies that printed my entire account number on the letter, which usually makes me grumpy at least.... My only question is how many people got someone elses letter.