I think I remember being attacked by sleepers in Balmora when I used to play Morrowind. On Morroblivion's main quest I saw clothless sleeper cult people in caves, but I never saw normal people 'pulled over to the dark side' and come attack me.
I think this is a bug, if I'm remembering correctly.
EDIT:
Uhh... I can't seem to edit this as fixed / closed... But it is, or should be...

#1
I asume you mean the thing where a sleeper tries to kill you when you sleep? There is at least part of the script active, as I have gotten the message when I wake up ("A dark force aproaches" or something to that effect) but almost never have I gotten the sleeper spawning anywhere near me, occasionaly they would appear outside of wherever I was sleeping but mostly it was just a message that popped up on-screen.
Not sure how close the sleeper is spawned or if it's an actual citizen that 'turns' but in the latter case it might very well be a case of pathfinding messing it up.