Necromancy is always evil in Pathfinder.
Necromancy is a great tool as long as you dont let your creations kill the townsfolk. I have a bone oracle that animates new friends all the time.
Thread necro or spell necro?
EDIT:LOL ninja'd be 8 seconds.
When is it acceptable to necro?
When you have something to add to the discussion.
When is it unacceptable?
O.o
When you don't.
Some will complain if you do, and some if you do not.
If the question has been answered in the thread, and you try to question it just because you don't like the answer then don't necro it. Discussing it more will not make the answer magically change. If it is a non-rules based question then I see no problem with the necro no matter how old it is.
Okay, now nobody say anything more on this subject for like...two years. Then you can go wild.