I was trying to get an NPC to move away from a bookshelf in the Vivec Library, and although the spell duration was only 3 seconds, whenever I try to leave, he follows me out the door. He DOES NOT, however, follow me in a given cell. I have yet to try using a door that's not near him, but even so, this shouldn't happen.

Open the console and type ra. That should get them back to their normal place.

As I expected, this didn't work.
Exiting a further door DID work, but only so long as I didn't use a door near him.
sethealth 0, resurrect didn't work.

However, I did discover a method that works (and a variant should even work on the X-Box, amazingly).

-Get sufficient Chameleon spells that you can attack without being accused of a crime. It should work to simply set your Sneak level to 1000 or so, but I didn't try this.
-Select hand-to-hand.
-Attack the NPC until they consider you to be hostile. I tried taunting, and also startcombat, but these didn't work.
-Open the console, click on the NPC, and type stopcombat. On an X-Box, use a Calm Humanoid spell, and the Intimidate persuasion option.
-The NPC should no longer follow you.

Wow. That's a lot to do!