Well if it vector data, the "tiles" can simply be a region of a sphere. That alone is not a reason for Mercator. There may be efficiencies of panning a flat pr

Well if it vector data, the "tiles" can simply be a region of a sphere. That alone is not a reason for Mercator. There may be efficiencies of panning a flat projection, but that is becoming a smaller and smaller issue as devices get more capable. Also, even when in "map mode", you will often notice that google maps is doing more than that. Go to a place where there are tall buildings (I'm looking at downtown san francisco) and you can see the perspective shift on the buildings as it pans.