Of course if I was going to buy a piece of excrement, I'd prefer to invest in the original idea by Piero Manzoni. Almost half a century ago, Manzoni crapped in a can and people bought it.
At least that piece is small enough to be hidden on a shelf or in a safe deposit box. The Serrano piece begs to be displayed, perhaps in the den? So what happens when the collector visits that room a few years from now and has the sudden flash of insight that the spectacular and expensive photograph on the wall is actually a giant load of crap?