Assuming scai's correct, it's It's the outline of of where Bing had high-res imagery at some point in the dim and distant past. You could argue that it never belonged in OSM in the first place, and it certainly doesn't now when there are many more imagery options.

Assuming scai's correct, it's the outline of of where Bing had high-res imagery at some point in the dim and distant past. You could argue that it never belonged in OSM in the first place, and it certainly doesn't now when there are many more imagery options.