I think most people, me included, underestimate the scale of the operation. When you hear "company will use private data to do X", you imagine what a reasonable person would do, like random sample a few conversations here and there. In reality they record everything permanently over months and years, far beyond what would be necessary to run the service.

It's kind of crazy how we get this level of surveillance while still having software that will lose your data if you don't hit Save often enough.