Human beings don't want to just enjoy something by themselves. They want to share that emotion - they want everyone around them to enjoy it like they enjoy it or hate it like they hate it. That's what makes a video spread.
“The vast majority of prisoners at Abu Ghraib, even after interrogation, had no further intel value whatsoever.”
“Why has government been instituted at all? Because the passions of man will not conform to the dictates of reason and justice without constraint.”