No idea. It just showed up in the mail. I used to throw those out all the time but I'm now paying attention, to the Citi ones at least.

There was no balance transfer fee. It's not universal default either, where a missed payment on any account in your credit report jacks up your rate.

Full disclosure: I do own some Citi stock (and BofA too).

I still can't figure out how they make any money out of this, as long as you steer clear of the pitfalls.