Here's another "bug" I noticed today: if your browser window is "too narrow", for example because you're using that widescreen to have two windows open at once, you get a horizontal scrollbar and ads display like this:
Yes, someone's being charged for an ad where even if I scroll I can only see a few pixels on the left. If I make the window a bit narrower I don't see it at all, but it's presumably still an "impression".
http://chunk.io/f/d1c9168e2f0c41edb8ea4bf3d29ddadc.png
scroll to the right and you get this:
http://chunk.io/f/f6020ad14aa84a6c9a3415291cfbb920.png
Yes, someone's being charged for an ad where even if I scroll I can only see a few pixels on the left. If I make the window a bit narrower I don't see it at all, but it's presumably still an "impression".