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.

Comments:
Nicole Miller
09/22/2012 02:29 am
This stuff is showing up on regular pc's as well. Until they go away, I'm removing them from my site. It looks like crap.
Nitajk
09/22/2012 08:47 am
I am getting dotted arrows on google ad sense ads. No idea why they are appearing. On a normal pc. Tried changing the code, but it is of no use. Looks like google ads have something different about them now.