I'm definitely not seeing that behavior. There was a pop-over ad that I had to skip though. I guess if that were malfunctioning / transparent, you wouldn't realize there was an ad frame hovering over the text?
Perhaps I wasn't clear. It's not the white background, it's the patterned background to the right and left of the content area. To be more precise, they have two div's with class "skinClick" setup on the right and left of the "content" div. You click on either one of those and it's the same as having clicked on the ad just below the nav-bar.
I tested in Safari, Firefox, IE and Chrome, same behavior. There's also the "Wait, your page is loading" popup ad you mentioned.
As an advertiser I would feel defrauded. Not one person clicking on the background is doing so out of interest in the advertiser's product.
How common is this practice?