I'm seeing some 468x60 Bing ads appearing over youtube videos that are extremely clever in design.
Google places the word "advertisement" in the lower right corner so microsoft placed the word "Microsoft" on the creative in the same font/color right beside it to make you think it's a Microsoft ad, it reads "Microsoft advertisement".
Then there's a big Bing logo on the left with the word video next to it and a button that says "play" and the entire ad has a border that isn't visible. The result is it looks like video controls of some sort.
A+ for design, I actually felt compelled to go check out bing videos and as a webmaster I'm sensitive to and avoid most ads. Too bad I found Youtube videos on Bing, lol.