This is incredibly timely for me, as I just installed a new theme from ThemeForest with all sorts of whistles and bells we don't need and shouldn't use b/c we'll never be able to undo using them if we switch themes again in the future. But the reason I chose it was incredibly simple: it has a sidebar (out of the box) that's wide enough for standard display ads. A good 95% of themes don't. And of those 95%, maybe half have a sidebar it's not incredibly difficult to change.

Sure, many other factors help me decide on a theme, but without the ad revenue, there's no site to put a theme on.

@bellasys - I agree with so much of what you've said here. Our team regularly laughs (in that bitter, ironic way) that the only people making money off our site are our hosting company and theme/plugin designers. Unless one of us picks up those skills or inherits a server farm, however, we're kind of stuck making the best of things.