I got this piece of mail today, and just as I was about to open it, I noticed a dark area near the "DO NOT FOLD" instruction.

 

At first I thought it might just be some dirt from the mail processing equipment.  But then I noticed that the marks seemed much more purposeful and seemed to be targeted at an area that often holds credit cards. 

I looked more closely, it seemed increasingly likely that someone had taken the envelope, and run a light pencil over it to obtain the embossed name and credit card number.  I started to wonder if this could be a variation of the gift card attack we read about during the holidays. The attackers could get my name, credit card number, and expiration, and then wait for me to activate the card. 

I wasn't expecting any credit cards in the mail, so the mail seemed out of place. Identity theft is always possible, but having just gotten new credit cards (and the fact that the letter was addressed to me, "Or Current Resident") I thought there might be another explanation. I took a closer look and noticed that the smears seemed to be dithered.  A close-up of the dark area looked like this:

This dark area on my mail was not an attack, but placed there by the sender. I assume they wanted to increase the chances that people would see the "attack", then panic and open this letter before others. Perhaps in a moment of relief, they'd call and order insurance.  Or maybe the sender just wanted people to think "Ah, I can go more into debt now with the new credit card that's surely inside! Praise the credit card companies!"

At it turns out, the letter was really junk mail from Geico, inviting me to be their customer.

I'll take a pass.