Subpoenas are irrelevant when they are siphoning all the data they can get their hands on through programs like PRISM enabled by Patriot act.
And yes, while it doesn't matter what they can and cannot do with your data now (unless you're a criminal not much, obviously), if the government ever becomes excessively authoritarian and dictatorial, keep in mind they can retroactively go through all the data they ever gathered on you and find something to string you up with.
And yes, while it doesn't matter what they can and cannot do with your data now (unless you're a criminal not much, obviously), if the government ever becomes excessively authoritarian and dictatorial, keep in mind they can retroactively go through all the data they ever gathered on you and find something to string you up with.