I guess the metro areas have more detailed satellite photos. On mine, I can see my house clear enough to know when the picture was taken: probably August of '05, after the new stoop was in but before I built the table for the deck and bricked in the back yard.
Yeah, I guess google gets these photos off of city and government databases and such, so many rural areas aren't covered all that well. My parents home is in the next city, and it is in hi rez. The annoying thing for me is the high rez images stop right on the edge of my town!