I don't think that "prevent rapey rapists from using your modelling site to do more rapes like they did using your site in the very recent past" should even be controversial.
That said...
Facebook, Google, and Craigslist are desperate to prevent her from seeking damages; the three companies claimed in a court brief that such a decision would have a "chilling effect" on the web and inhibit free speech.
Because of this I strongly suspect the aforementioned big players will try to have the case appealed and they have deep pockets.
Which is really stupid. Once they have knowledge* that the rapists had done this before, they knew that he could do it again, and had a duty to the plaintiff to warn her of dangers associated with using their service. If this were purely done in real life, there wouldn't even be a question of tort liability on the part of the website owner, as this is textbook negligence. In fact, there is a tort called "negligent referral" in which doctors and lawyers can be held liable for referring a potential client to another doctor/lawyer that the first doctor/lawyer knew did not operate according to the standards of care. Literally, I could be held liable for something far less damaging than what this woman endured.
*This is only at the complaint stage, and most lawyers at this point will claim the defendant had knowledge, even if they didn't. They do this because it is necessary to save the complaint from a 12(b)(6) motion to dismiss, and because discovery may show that the site did have that knowledge. At the complaint stage, the allegations of the plaintiff are taken as true. After or during discovery, the defendant can dismiss the case under summary judgment if it can show that there is "no issue of material fact and that defendant should win as a matter of law." These are two vehicles used by the court to dismiss flawed cases before trial. So, for purposes of the thread, I'll assume that the site did know about the rapists beforehand, because I feel this discussion is less about legal standards (what Plaintiffs can prove and when plaintiffs can prove it) and more about the extent websites can be liable.
I don't think that "prevent rapey rapists from using your modelling site to do more rapes like they did using your site in the very recent past" should even be controversial.
"Prevent rape" is not controversial because it's not actually policy, it's a desired end result.
How should Model Mayhem have acted? That's a more interesting question, I think. Warn users, ok.
1. Prevent rape is not the desired end. The desired end to hold the site liable for its failure to acting irresponsibly in a manner that injured a woman in the community. The site knew of the rapists beforehand. At this point, it had a duty to ANYONE using ITS SERVICE to warn of potential dangers. It would be no different if we replaced rapists with robbers, assailants, or murderers. The desired end is to get the website to say "hey, we know these people are bad eggs or had complaints of serious wrong doing against them for their use on our server; you should know about this before you meet them."
2. Specifically, torts are comprised of four elements: a duty, a breach, an injury, and a cause. Once an actor has knowledge of a danger, it has a duty to warn others of the duty. The website knew. The website did not warn her, constituting a breach. She was raped, constituting an injury. That leaves cause. Now, it is a mistake to focus on whether the rape itself was caused by the site, that is NOT what the law asks. The proper question is whether she would've gone to the rape-session-photo-shoot if she had known that the cameramen who called her had a history of drugging and raping women. If so, then the actions of the website were a partial cause for her injuries. Again, she is NOT suing them for the rape. She could've been raped by first time rapists she met at a Starbucks. She is suing them for their negligence which contributed to it. Again, this is a text book case of negligence.
3. FB and the other sites are making much ado about nothing, because this isn't liability for any injury, but only injuries done by people that the site knew were a danger. The site could set up a function warning users that certain people have had complaints against them. The site could hand out bans or temp bans until the facts are discovered. Sites like Model Mayhem could issue background checks for its photographers before letting them use the service.
ETA: and the thread title is misleading. The 9th Circuit simply said that she COULD sue because her motion survived 12(b)(6) scrutiny, also known as the motion to dismiss stage. Specifically, the parties go to trial, the lawyers do their talking, defendants filed for a motion to dismiss, and the court said no. At this point, the defendants appealed and the Ninth District said "Frig off Ricky." So, now the case is sent back to the district court to proceed as it normally would, through discovery, and onto trial. Her suit is not successful, but this makes it considerably more likely that the case will settle.