I have mine under the post header (but mine are custom post types, and not like blog posts) and made sure to put enough space between the social buttons and the ads so there couldn't be any accidental clicks.
Dunno how it affects CTR - could be a lot, could be not at all. It's definitely another distraction. But everyone who shares something of mine on Twitter or Facebook tends to bring in a few more users, who then are likely to come back, and ever so slightly increase my brand and reduce my dependency on Google. So overall, if I have to give up a few bucks worth of clicks to get that, I'm okay with it.