>I've heard folks suggest that mounting the ground up 'protects' things by making something dropped and hitting an exposed plug tab less dangerous since it hits the ground first. I think that's kind of reaching for a reason, myself.
My brother welded a dime to a terminal when it got between the plug and the socket. Fortunately, it burned off of one of the terminals almost immediately, but was pretty well stuck to the other. I thought it was a silly idea too until I saw the results in my own home.