I don't think ANY registry should accept registration from puppy mills. The AKC trots out the "Oh, we are just a registry! Poor, helpless us!" line every time their greed gets the upperhand.
I recall once before the AKC decided to register Petland's puppy mill puppies . . . Plenty of breed club members (officers) were upset and angry, asking how this promoted or protected purebred dogs. The "main" AKC officers' replies were all couched in terms of dollars and cents, plus a few weak justifications like "People will research the AKC when they buy an AKC dog and become super-knowledgeable about purebreds and better breeding!" (Please.) Mostly they just talked about the revenue it would bring in. I'm disgusted that they've tried again, after all the outcry last time, and apparently (if what this blog says is true) have at last succeeded.
The AKC is a registry, but they aren't "just" a registry. They are the best known dog registry in the US. Every company has a "brand", from McDonalds to the Red Cross to the Boy Scouts. When the Red Cross puts their name, their brand, their reputation behind a rescue effort, there's immediate recognition. People think, "Oh, it's legitimate. They're with the Red Cross." When the AKC lends their name to puppy millers pumping out puppies, that gives pet stores more legitimacy in the eyes of the public. No responsible registry should be shaking hands with puppy mills, but when the AKC does it, more damage is done.
With great power comes great responsibility.