Granted, we do have the occassional Watchtower or Mormom missionaries but they're aren't very aggressive. On the more sinister side, in the passed four years two homes have been hit by ice falling falling from aicraft.
I guess statistically getting hysterical over the police and my home just isn't a concern (which come to think of it, doesn't seem to be a major worry for the general public at large either) but perhaps I should invest in a metal roof.
Especially not if you answer the door butt naked. Not that I've ever done that, of course....
There was a hilarious thread on FR a while back on how to deal with Jehova's Witnesses. I'll ping you if I find it.