Apparently there's a new wave of beheadings going on worldwide -- terrorists like the shock value that cutting off someone's head has. Three policemen in Haiti were found headless; it's being called Operation Baghdad. Meanwhile, people online are collecting and disseminating these images -- which I personally don't want to see; much as it seems to be one of the defining images of our time (yay!), I'm just not masochistic enough to want this stuff rattling around in my head. I watched the Berg video until they took out the knife -- then I left the room while a friend of mine finished it. The sounds were bad enough.
There's a history of beheadings here, if you like.
I recall somewhere reading that often when heads were cut off by guillotine they would blink and show signs of life for some time after being removed.