I’ve been asked by a couple of people what I mean by a direct connection between Azog and the Necromancer. If I’m right, this is a big ol’ spoiler, so I’ll write it in the comment to this entry, and if you don’t want to see it, don’t read the comment.
Scratchings
David Scott Marley's online journal
Scratchings 
On the one hand, we have a character who at the start of the movie is believed to be long dead, who Thorin in fact says cannot possibly be alive.
On the other hand, we have a character who is said by the locals — though Saruman pooh-poohs the idea — to be able to raise the dead.
So. Do we think these two guys know each other or not?
Agree entirely.
Actually, I find this development of the relationship between Thorin and Azog one of the most interesting things they’ve done.