From what Google's said, it appears the government can't arbitrarily query Google's servers. Google has stated pretty clearly that someone at Google has to check off before an account is pushed to a machine that the government can access and that the data cannot be accessed without this happening.

That's Google. We've yet to hear from many of the other companies in the program about whether this sort of access is technically impossible, or whether it's an honor system that the government is supposed to follow.[1] I haven't been closely following the Facebook, Microsoft, or Apple statements, so maybe they have also been explicit that it is a restriction that is implemented by technical means. Some of the companies haven't said anything yet.

How many of the companies really make sure there is legitimate documentation for each request? Do they really do this every time, or have they become resigned to the fact that there's nothing they can do, so they just rubber stamp each request coming through, even without the proper legal documentation?

[1] This seems to be a major issue--the President and NSA leaders have claimed that analysts "cannot" access your phone metadata and phone call content without the correct legal instruments. But by "cannot", they seem to mean "they are not allowed to" rather than "it is not possible for them to".