I am aware that this is almost “common knowledge” by now, but I would like to remind everyone that the U.S. government is spying in almost all parts of the daily live of American citizens (and non citizens as well, for that matter 
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They apparently built several “secret rooms” in various places in the US to get access to the vast majority of internet traffic in the USA.
One of those facilities is in San Francisco in Folsom Street, in the AT&T floors. A quick summary is available on Wikipedia:
http://en.wikipedia.org/wiki/Room_641A
The guy who revealed this was Mark Klein, he worked at AT&T and was suspicious about dubious and illegal activities at his work place. He came forward and made his findings public:
http://www.pbs.org/wgbh/pages/frontline/homefront/interviews/klein.html
This is what Klein thinks about this kind of surveillance:
>>That’s right. They have no way of sifting it out unless they look through it later. Now they can claim, “Oh, we are right as rain; we’re only doing the legal thing and selecting out a few people that we’re legally entitled to,” but that’s only after they get all the data. The analogy I use: If the government claims, “Well, when you do your taxes, why don’t you just write me a blank check and we’ll fill in the amount? Don’t worry. We’ll do it legal. We’ll fill in the right amount,” would you do that? Nobody would trust the government by writing a blank check to them. It’s the same thing with the data we’re giving them. …
When the founders wrote the Fourth Amendment, they had a specific antagonism against what were called general warrants, as you might know. General warrants is when the British troops would come in with a warrant and say: “We have the right to search your house. We’re looking for something. Looking for what? We can’t tell you. We’re going to ransack your house.” That’s a general warrant. They can turn your life upside down, and the colonialists [sic] hated that.
So the Fourth Amendment specifically bans general warrants. It calls for specific warrants in which the things to be seized and the persons to be seized are specifically named. There’s a reason for that. It’s to protect against arbitrary government power. And what they’ve done is to trample over the Fourth Amendment by basically instituting a general warrant on the Internet.<<