My wife got one of those letters last week. It was something that was made to look like a check for close to $2500, but if you looked close enough, it was a "voucher" for trade-in value or something like that. And it also said "YOU HAVE WON!" one of the following prizes. Of course, there was one new car prize, and then like a $500 gift certificate, and a $20 gift certificate, etc. Guess which one we'd have gotten if we showed up? (and then probably only if we demanded it)
The FUNNY part of the whole thing was that it was for "being a loyal Nissan customer!"
My wife has owned one Nissan. She bought it new in 1991 and traded it off in 1994. "Loyal."