I don't care one bit. I could see how certain signatures on certain cars might add a bit of appeal/value, but only in a very specific set of circumstances.

There was a guy in Hemmings selling a street rod, and he put in the ad "Glovebox signed by Butch Patrick (Eddie Munster)." It wasn't a Munster Koach or Drag-U-La, just some generic street rod. Who cares? In fact, now I have to repaint the glove box door if I buy it, so it's not a selling point, it's a detractor.