And, if you become aware of sex trafficking on your website and you don't do anything about it, you are absolutely complicit. This is hardly rocket science, and it doesn't seem to overreach the way everyone is screaming that it does.
Edit: see also willful blindness. https://en.m.wikipedia.org/wiki/Willful_blindness#Precedent_...
A famous example of such a defense being denied occurred in In re Aimster Copyright Litigation, in which the defendants argued that the file-swapping technology was designed in such a way that they had no way of monitoring the content of swapped files. They suggested that their inability to monitor the activities of users meant that they could not be contributing to copyright infringement by the users. The court held that this was willful blindness on the defendant's part and would not constitute a defense to a claim of contributory infringement.
It would seem ridiculous for courts to start charging e-mail providers, for example, as facilitating sex trafficking though, even if they must suspect their services are used for such activity. I wonder how it will play out.
I suggest you read previous threads on this from a couple of days ago. They had detailed discussion on the changes in the wording, from being "participant in sex trafficking", where you somehow benefit by actively encouraging the activity, to "facilitate sex trafficking", which is not fully defined.
Basically, the concern is that if Craigslist knew that their site was used to deal with trafficked persons, even only in theory, they are facilitating. Any open forum will thus require enormous resources to actively police, or you can't have an open forum.
However, the wording of this law suggests that less extreme measures, such as an automatic filtering system and user-report functionality, would leave craigslist liable. Note that the personal section was (probably) not majority prostitution. It was a place where prostitution would happen. It seems to me the situation were different if the personal section was 50% prostitution or more. Question is, does section 230 still protect those who operate a site where 50% of user-generated content is illegal? Because if not, I don't see how this law is necessary.
As long as you're willing to risk paying requisite attorney fees. Craigslist apparently wasn't.