The other answers have covered much of it. As someone who has handled FTC investigations and spoken with them on enforcement priorities, their mantra is that a data breach does not automatically trigger an investigation but that the absence of a breach does not protect you either if you are not providing adequate security for the type of data you are collecting.
Note that cyber insurance products are increasingly becoming more affordable, but be wary of the exclusions.
It depends on the nature of what is published. If it was subject to any court order or is itself public record information. They have a First Amendment right to publish material, so the analysis really goes to each item published.
If you are a victim of cyberstalking you should consult with lawyers in your jurisdiction that handle these type of claims. for example Working to Halt Online Abuse (WHOA) has a list of lawyers who handle these cases: Its important that they be familiar with the civil and criminal penalties available.
It violates their terms of service, is considered deceptive advertising by the Federal Trade Commission and could violate your code of ethics if you are a doctor, chiropractor etc. In addition, your competitors could sue you for this practice, so its little gain for high risk.
As the others have indicated, you have waded into the area of identity theft and cyber harassment both of which have criminal and civil implications (California also has a law about e-personation that recently went into effect). You should consult counsel for any further information.
I have worked with dating sites and my concern would be the business fall out if people knew the bios were ghost-written. People draw clues from how people tell things and not just the substance delivered, you are spending money to eliminate clues that might be valuable to your clients.
Marc has done some good work in this area. The other lawyers are basically right - section 230 applies regardless of the domicile of the website. Even still, the analysis will depend on the specific facts as revenge porn plaintiffs are trying to argue that revenge porn sites are content creators by the way the sites are set up and content solicited and outside the reach of Section 230 immunity.
You have to assess this objectively. What is being posted? Is it a statement of fact (even if false) or opinion? If its opinion, there is little you can do. If factual in nature, what are the damages and can you prove them. Then take that number and weight it against the cost of litigating and toll that would have. Finally, talk to reputation management people who might be able to advise you how to bury the negative content with positive content.