Harry Potter Theory: Why Didn't Voldemort Return as a Ghost?!

Go to http://candidco.com/scb and use code SCB to get $75 off! Voldemort fears death ABOVE all else... And we know that ghosts are people who either feared death or had unfinished business on earth. Why doesn't the Dark Lord return to haunt Harry?! Or better yet... is it even possible that he could?!