Public opinion is shaped a great deal by what and in what way the mass media covers a specific topic. There was a lot of uproar about NSA surveillance while it was in the news, which quickly died down as the headlines disappeared. Out of sight, out of mind.

And then there's also the thing that, arguably, Google and FB give those people something in return which they might consider worthwhile for just data. I'd question that the majority of the user population is aware of the implications of handing over data about themselves and specifically other people, who may or may not be okay with that.