Dudes do this to me at work! If I'm looking up something for them at one of the computer terminals around the store (not the info desk one, since they're not allowed behind the counter), they will stand riiiiight next to/behind me, trying to read over my shoulder. Women do it to, but it's mostly men. I'm always like, dude, you're in my bubble. I have yet to find a way to tell them to back off politely. :\