What is Google doing with the data? Who has access to it? How do they make sure it doesn't fall into the wrong hands?
And if you say the difference is that you're surrendering your data to Google voluntarily, I'll say it's not that different from what you do with the phone companies. What you had here was lack of information. You simply didn't know the government was collecting your data. Well, now you do. Most Google users aren't aware that Google is actively scanning and analyzing their information either. The only difference is that the US government owes the people an explanation, while Google reports to no one, as long as its egregious widespread surveillance - which, BTW, is on a much bigger scale than this NSA business - is considered legal. The only reason Google gets away with it is because people either don't know, or would rather not know how their personal information is used by Google (I would add "against them", but that is a metter of opinion).