backpage had been doing its business in the open in USA for almost 10 years when it became client of Salesforce in 2013. So, until 2018 no DA was bothered by the human trafficking supposedly rampant on backpage during that time, while it sounds that it was Salesforce's burden to do that the DAs hadn't and wouldn't for years - i.e. to perform investigation, etc.
Do we really want a massive SaaS company to criminally investigate its clients at its own initiative? May be it is exactly what we want - I think there is a massive attack across the board on the provider safe harbor principle with the goal to scare the providers into skittish self-censorship which the most and foremost would affect the basic civic freedoms.