Government is hardly the largest consumer of online data. Instead it's Google, Yahoo and advertisers focused on reaching persuadable audiences at minimum cost are the largest producers,
I know of no guarantee of privacy or reasonable expectation of it for anything posted on Facewbook or Twitter - indeed both are ostensibly dedicated to wide area broadcast of data posted by users - privacy is the antithesis of their function.
Obamacare now gives government complete access to all details of your health care. Are you concerned about that? I find the evident concern about the government's collection of metadata (call, internet traffic data based on ip address and telephone number) for national security reasons, coupled with apparent indifference ot other sources a bit odd.
I also believe that the question of legality here trumps the question of ethics. Just what ethical principles do you have in mind?