Interesting. I'm assuming there will be areas that we are prohibited from imaging. Will these be limited to areas defined by the US Government or every government that Google works with?
They likely can take images of everywhere in the world. They will very likely be limited as to who they can sell certain areas to, at various resolutions. The US government restricts sale of imagery under 31cm resolution currently, but previously it was 50cm. Neither of those restrictions would apply to these satellites which are 90cm resolution, but similar things will probably apply elsewhere. I believe Israel is one of those places with a coarser limit in place.
Having worked in this area, I can say you are on the right track. Not only the US, there are many countries/powers that will get very upset if certain people see certain areas.
As for who gets to see what, there are extremely stringent rules set by many of these governments; even within government organizations themselves, there is huge variation in access constraints.
This seems strange to me, considering there is high resolution "birds eye"(taken from a plane) imagery of a variety of sensitive US installations available on Bing, not to mention what's on Google Maps/Earth. There are other sources as well.