I have two sites that get a majority of visitors through mobile. I have a responsive theme on one, and the other has a theme that looks the same when it shrinks down to a smartphone, but is mobile-friendly. The responsive site just ignores a couple of my ads and loads the others way below the content. Since I don't use Adsense, I have no tech issues - on the regular site, my ad providers even detect mobile and throw in 320x50 ads without being told.
But the responsive theme doesn't let the ad providers recognize that it's a mobile user, so they just get the regular ads. Sounds good in theory, but:
--What if ad networks get smarter at serving ads to target mobile users? Then the responsive theme won't cooperate, but the mobile-friendly non-responsive one will.
--What happens when advertisers notice that responsive themes are loading the ads at the bottom, where no one's likely to notice them?
--And then there's the fact you can set your phone to be detected NOT as mobile so you get the normal website. I'm not sure how these users are handled.
I think responsive is a great option for a site without ads - e-commerce, corporate, etc. I'm just not sure it's right for ad-monetized sites. The phones are really good at handling site designs that are flash-free and that don't block re-sizing (trufax, I have come across sites that do this somehow). Even as a user, I'm just not sure I like the responsive theme.