It's specific to the type of information that is available to Google at a whim vs. the NSA. There's simply no comparison there...Google, while quite far reaching, is not getting to the level of information that the NSA is privy to if they want to be. Google primarily focuses on advertising and money...if they're making a dime, that is where their focus is. NSA is focused on the entire SPECTRUM of information that you have ever put online, and that is creepy as hell. We're not talking your purchase trends online...we're talking every little detail of information you've ever shared, applied for, uploaded, downloaded, commented on, etc...your entire e-life. It's accumulated to an absolutely ridiculous point...and used in whatever fashion they see fit.
Imagine it kind of like this...think of a person who knows you the best and has known you that way the longest. The details they can recall, the traits they know you have and the history that person can recall about you. Now think about a co-worker or neighbor that has met you a few times and might see you a couple of times per week. The first person is not even on the level of the NSA...the second person is Google.