The real life ménage-à-trois can be awkward and complicated, if not emotionally then definitely physically. But if nothing else, an extra naked dude is always good for making a sexy scene look all the sexier.
One may find this particular threesome a little disappointing if only because the third guy doesn't actually do anything. But then, the two guys fucking seem to be getting along just fine on their own, and we kind of love watching him walk around in the background, casually showing off his chiseled abs and massive dick. Just having that extra slab of beef in the room adds a subtle hint of debauchery to the whole affair.
Incidentally, while we still are adamantly against the tramp stamp, we actually didn't mind this guy's ass stamp at all.