The list of names released by Anonymous won't be considered authoritative.
A 'sex offender registry' is a whole different problem. Don't want to troll here, but please understand that in a global forum like this a remark a la 'at the very least' combined with a debatable ~local~ set of law(s) is a dangerous thing. In other words: No, I hope that at the very least no one ends up in any registry.
I'm all for prosecuting/convicting these people. I'm against any kind of (public) register, period.
"Studies and case reports indicate that 30% to 80% of individuals who viewed child pornography and 76% of individuals who were arrested for Internet child pornography had molested a child. It is difficult to know how many people progress from computerized pedophilia to physical acts against children and how many would have progressed to physical acts without the computer being involved. It is interesting that the NIBRS data from 2000 show that most child pornography crimes reported did not involve a computer or the Internet but were related to photographs, magazines, and videos."
So while it's seems undeniably true that many users of child pornography sites are child molesters, I'm not sure that "stop at" has the right progression. I presume the more common case is that real life molesters are attracted to illegal sites, rather than that casual online viewers become criminals.
Consider applying the same logic to heterosexual adult pornography sites, which are also illegal in some jurisdictions. I'd presume that the majority of individuals viewing such sites have also engaged in adult heterosexual behaviour, but I'd probably assign the causation in the other direction.
As honeypots, though, the sites seem like great bait. But where's the line, and what should the response be. I've recently bought lye (for brining olives), sulfuric acid (for scarifying seeds), controlled antihistamines (for allergies) and looked at Erowid (for trying to understand SSRI's). How much intense police interest do I deserve for my "obvious" profile as a meth producer? Which, to be very clear, I'm not.
More seriously, you hit on the problem, which is that a lot of people seem to be assuming that Anonymous' vigilante justice is error free. Those that are wrongfully accused of using child porn could have their lives seriously damaged.