Yes, but I think that Janus is now thinking about a house rule now.
Personally I'd consider charging ubernegative NPCs extra fate points to buy out of compels.
One thing I want to make clear, when I talk about an NPC with negative refresh, I mean an NPC that has spent more points on powers and stunts than it can afford with its base refresh. It isn't so much a balancing mechanism (total points spent on powers/stunts determines actual power) as it is a measure of how much control the NPC has over its nature.
Think of a character who picks up a Denarius while at a +1 total refresh. At first he resists the Fallen and maintains his positive refresh. Eventually our tragic anti-hero gives in and buys Hellfire at the angel's urging, bringing him to -1. Sure, he's an NPC, but he isn't going to go around slaughtering his friends and family for no good reason. He might even help out his former comrades from time to time. As time goes buy the Fallen helps him master his magic, and he buys four more points of refinements, for a total of -5. At this point he's pretty far gone, but still recognizably the same person he was. Twisted and evil, yes, but still the same person. Then he goes hog wild and takes all the shapeshifting powers, bringing him to a total of -15. Ouch. At that point I'd say the person he was is gone, entirely under the thrall of his Fallen.
Come to think of it, I'd say that the Denarians who keep their human names probably don't have substantially negative refresh totals.