As for erasers, it's been a long time since I used one to clean contacts, but I do remember turning gold plated contacts silver. I think I erased the thin gold plating off.
I guess you have to be careful anytime you use anything abrasive to clean contacts... unless it's one of those carts that won't respond to anything and has visible corrosion on the contacts. For those, anything short of sandblasting barely makes a difference.













