But, recalling what the bad-driving site was an analogy for, it doesn't seem like it would be appropriate for sex workers sharing reports of bad clients.
As it is, libel laws give you protection if you can prove the claims are false, and you can get civil damages if you show harm. What would you say should be legislated beyond that?
It's not an easy decision, but I lean towards "should be illegal if done anonymously and without proof".
Would it be a civil thing where you could sue me for some amount, or would you make it a criminal infraction?
I'm pretty sure that "no anonymous slander" reduces the amount rapidly, so you end up with a bunch of legitimate accusations that people are willing to stand for because they can provide evidence. The whole "I don't like his hair, so I'm going to make up stories about him" stuff goes away.