[ls65536]

In my view, this is really the more important and unfortunately often underappreciated concern here. There's a lot of talk about what personal data might be captured by these apps/services (not to minimize that either), but it seems there's overall much less discussion about the potential for the control of information/ideas over large audiences, even in subtle but impactful ways. Not only is it plausible that such interference could happen, be it to exert political or economic influence, but it's likely that it could be done surreptitiously with little to no oversight by regulators, governments and ultimately the people using these services.