It appears Google is testing showing a new form of large blue arrows on AdSense ads when viewed on an iPad and iPhone. I suspect it shows for all iOS devices and maybe even all smartphones and tablet devices.
Although I did not test Android or other smartphone devices, I do suspect this is a new form of mobile ad unit designs.
I was able to replicate this on my iPad and here are a couple of screen shots of it in action.
I should note, the blue arrows are large and pretty bold on the page, especially on sites where the ton is not blue.
Now, this isn't exactly new. Google was testing a different form of these blue arrows back about 9 months ago.
Maybe now Google made it official?
Forum discussion at WebmasterWorld.