I've had it happen to me, too. The person listed on the PIN code offer was a friend I went to WDW with in 1996. Every couple years, I've gotten a pin code with my friend's name on it, but I never wanted to use it anyway.
My guess is that they are sending pin codes to all the secondary names on prior guest reservations because those names haven't popped up as recent visitors. Primary names (like ours) have visited more regularly, so we don't get the pin codes.
In order for Disney to stop alienating the rest of us, they would need to cross reference the addresses on the PIN code list with guests who do go more frequently and eliminate the secondary vs. primary guest glitches.
By trying to entice the "We want you back!" crowd, they are alienating the "We have you already" crowd by these computer glitches.