I see those in the junk boxes at coin shows and have to laugh everytime I see one. Painted quarters comes to mind.
I don't laugh when I see one, I'd actually like to pick one up for a $1 or 2...but any more than that it's too much money. IMHO, unless it is a contemporary plated example...then its nothing more than a damaged coin. It would be kind of neat to have one just because of the story behind it...but I certainly wouldn't pay a premium for a modern plated coin.