I've noticed some areas have better resolution than others also.

Check out Newport News, Virginia: some areas are crisp and clean enough to see the color of an outboard motor on a boat, others are so fuzzy you can barely make out a street.

Also check out the state of Massachusetts - the image changes exactly at it's border with surrounding states. I have no theory for this at all.

I suspect it's more about the satellite coverage than anything else, but then why Massachusetts?

I've heard that it's not satellite coverage but the high detail is available where mapping photography from airplanes are available publicly.

Mark -
I agree that's where the really clear detail comes from (airplanes rather than satellites), but I don't think that explains the odd division near Newport News (which I think may be obfuscating part of the Naval Base), nor the sharp-edged borders around Massachusetts.

it makes sense, but it doesnt explain the extreme detail of other places, like along the peruvian and chilean coastlines, which clearly shows their Navy bases in extreme detail. ( apparently, and this is a surprise to me, they have both subs and dry docks!)

( also, check out their use of the hillsides for political campaign slogans, its a laugh!)