Does anybody know the accuracy of Google Earth, Google satellite, and Bing aerials, and at what scale? I think that you have different/better accuracy if you have subscribed to their professional version.
Both Google Earth and Bing map use data from different sources (satellite images and ortho-photos). The horizontal accuracy depends on the source of the datasets and the level of orthorectification. It is usually better near cities than "in the middle of nowhere", but it primarily depends on the data sources. For instance, some countries have agreements with those image providers to use their national ortho-photo basemaps. In this case, the geolocation accuracy can be as good as one meter (or even better). In other places, images are adjusted based on co-registration with reference data (e.g. Landsat composite) so that the accuracy is worse than 25 m. There were noticeable improvements of the geolocation accuracy since the first launch of those products, but I still found errors up to 50 meters last year in some remote areas (in Brazil and in Africa).