Am I being naive; I find it hard to believe that an area of Germany (along the Rhine) that I occasionally view with Google Earth hasn’t been updated since May2000. The area is rather populated; why wouldn’t such an area be revisited? The current resolution of the 2000 imaging is rather low res.
I don’t know about that particular area, but I have noticed areas where newer images are of poorer quality than the older images, and Google seems to be using the older (better) images. (For an example look at the city of Waveland, MS on Google Earth).
Google doesn’t collect the aerial photos themselves; they rely on various government agencies (and maybe some private companies?) who do aerial photography. These are generally ones involved in some sort of natural resource managment, so in this sense an area being populated might actually make it less likely that that aerial photography would be done there. I’m in a smallish city surrounded by National Forest land and there’s much newer and clearer imagery avaliable of the wilderness outside of town than the town itself.
Of course, there’s all sorts of international differences both in whether organizations do a lot of aerial photography and whether they release it. The US has always been pretty enthusiastic about maintaining and updating aerial imagery and is very liberal about letting the general public use them.
When the Isle of man first got high-res imagery (it had been years on google maps/earth with very low-res images) the image data it used was already over 6 years old.
It has since been updated. Current imagery is no older than about 2 years.