netmeg - 9:03 pm on Sep 21, 2011 (gmt 0)
I assume that the presumption is that if I go to a site and see that one of my friends +1'd an ad, I'd be tempted to click on it to see why. Which of course that site would be paid for, so it would encourage CTR.
It does work for FB likes, which is why I have big ugly FB boxes with faces on my sites, even though I dislike them myself.
I have no reason to think it would work with ads, but hey, I'll try anything once.