I don't understand how the government would be able to read all the stuff that is written on the internet, or have an effective program that looked for key words. The volume each day must be fairly large.
I am not savvy about what they can learn about me from my emails, the web sites I visit or the my posts on various discussion groups. It seems they would need to first make some sort of arrangement with my service provider. Everytime I log on, I get a different address assigned to me, so without help from my service provider how would they know anything other than the current ip address I am using for that log on. Maybe my emails they could somehow intercept since they have my return email address on them.
It seems to me the more they spy, if they can do so effectively, the more people they need to have to check the content of what they have gathered. I think maybe this spying stuff is like the IRS bluff where they every tax season have some high profile indictment of someone for tax crimes, but they just do not have the staff to much more than a relatively few investigations. Maybe they just spy on people like Princess Dianna or some vocal anti-government types who deliberately get in the news.
I don't really know, but if your name is not Mohammad then I doubt that you get any attention.
But just for a laugh go here for a parody on data mining:
http://www.aclu.org/pizza/images/screen.swf