EditorialGuy - 5:00 pm on Jul 7, 2013 (gmt 0)
Maybe they're testing? I just did a similar search, and the right-hand column was considerably narrower than the main or left column with the organic results.
I also did the same search on Yahoo!, where the ads in the left column had a white background and were almost indistinguishable from the organic results. (At least Google--like Bing, but unlike Yahoo-- uses a tint behind its ads in the left column. Of course, it would be even better if the ads in the right column also had a background tint on the SERPs of all three search engines.)