> My sense is that, in most cases, sex workers do not act as their own agents, so I see backpage as a platform catering to pimps et al.
Just fyi, you are mistaken. That is the whole reason they have to force/traffick people and trap them rather than just recruit. Anyone here legally and does that sort of sex work has mostly moved away from the pimps.
> Though I guess there's an argument to be made that sites like backpage make it easier for sex workers to disintermediate pimps, which I imagine would be a good thing.
Legal adult citizens who were prostitutes were doing exactly that.
Pretty much since "online personals" became a thing, sex workers quickly removed all the intermediaries beyond the ads.