apples and oranges, migeru -- I mean, it's a good thing that a modern hypodermic is nice and sharp and can deliver dental anaesthetic to my tooth roots with minimal gum damage, but that doesn't mean I would be happy about random jabs from sharps wielded by strangers or left lying about :-)  the turf-violation aspect obviously applies to involuntary exposure, not formalised and voluntary medical procedures...  more on (in)voluntary risk and perception later...

The difference between theory and practise in practise ...