Why don't you cite the law that makes this policy illegal? Section
230 of the Communications Decency act protects the owners of a website who publish information provided by others.
There have been a number of court cases involving ponzis on the forum and theymos (or the forum) were not held liable
Not sure if you're intentionally missing the point. The case law cited in your wiki article does not address knowingly facilitating illegal activities.
In other words, a website allowing users to post pictures & being 95% child porn is not going to benefit from Section 230 of the Communications Decency Act. Regardless of disclaimers.
Like I said in the past, the forum does not attempt to investigate if something is a scam or not therefore they do not have knowledge of illegal activity if there is any. Just because someone claims that something is illegal does not make it so. I ask again that you cite a law saying that the forum is breaking the law by not moderating scams.
Re. bitcointalk lawsuits: not you're referring to (links?), but the fact that theymos has not been charged with anything merely proves that bitcointalk is much more useful as a honypot, a place that a couple of fat LEO could monitor from the comfort of their office.
And providing a perfect paper trail to second-rate conmen, should their scams warrant sufficient interest.
As long as theymos cooperates, everything's fine. Thus far, he's been cooperative

I don't see your point here. So what if the forum is a de-facto honeypot? Don't break the law?
edit:
link to case regarding illegal activity on the forum