I've thought for a long time that 'big brother' will not come from governments, but from corporations.
A few of the many important differences:
1) Consent. No one is forcing me to use Google products. (Well, except my employer, which contracts with Google for email and various other services, but anything that they have access to is my employer's property anyway and I have no expectation of privacy to begin with.) I could completely banish Google from my personal life without severely impacting anything I do. It's a little more difficult to escape the reach of governments.
2) Competition. Microsoft and Yahoo would be happy to handle my email instead. I can't switch governments without physically moving to another country. (Voting doesn't count, and I don't vote anyway.) Conversely, it would not be a huge burden for me to jettison all Apple or Microsoft products, although it would be problematic for my music collection.
3) Force. Google does not have the ability to dispatch a SWAT team to break down my door, shoot my dog, and haul me out in handcuffs. And why would they, anyway? They don't care what activities I'm engaging in offline except for the purpose of targeting advertisements.
There are certainly all sorts of things that corporations can do to make our lives unpleasant, but it seems rather perverse to worry about creeping corporate dictatorship because of Google's ad targeting, especially given the track record of governments.