The idea that you need to be able to hide your political speech is a problem to start with. You won't be saved from tyranny by that power - if you use it, you already experience it and tyranny needs no reason to kick in doors beyond suspicion. Accurate intelligence is what you need when you're trying to do things right (or you've executed all the dissidents and the remaining ones are still a real threat).
Those who want to hide don't interest me. If there fears come to pass, I'll be long dead, and they'll have sat by and done nothing while it happened.
This is currently the case-- radical political ideas have been accompanied by state surveillance and attempts at discrediting for a long time, and the current crop of NSA totalitarianism is no different.
b^)
There was actually a practical example of a man FOIAing his documents from Facebook, which revealed that they had over a thousand pages specifically devoted to him alone on every facet of his life. Even though he was only a "casual" user (one wall update a week, or so). You can see it in the documentary film Terms and Conditions May Apply.
As for me personally, I've never had a Facebook account. Although virtually no one is impervious, reducing social media presence is still always useful to get rid of the blatantly incriminating things.
Unfortunately, the biggest threat is perhaps, what other people are saying about you. I have no idea about what's going on there...