I didn't get one today, but I got one not long after signing up with them. I think they send them out every once in a while just as a reminder. There was a thread the other day at mycoupons where someone asked if anyone had gotten a survey lately, and there were a log of responses to it so that may be why a letter was sent out.
We all get excited when we get a survey from them and usually post that we have gotten one, and I've wondered maybe if we aren't even supposed to do that?