THIS would be why I will not use plugins that don't offer the option to turn of said annoying advertising. WordPress rules or not. If you MUST, put the annoying ads in the admin backend where only the site owner has to suffer through them.
Though that, I understand, is also against the rules? Even so, I see plenty of it recently.
Really good (and useful to me) plugins, I will gladly pay for. Or even pay for a copyright-like link to be removed. If the plugin is really good, but has these annoying ads or obligatory copyright BS, I will just go find someone to make one for me just like it. Less the annoying ads (or whatever bloated crap they stuffed in).
Finally, I avoid Zemanta like the plague. It is one of the most insidious advertising platforms I can think of. Worse, I found it slows your site down (been a while since I tried it). So take note of that! These 3rd party ad type plugins spend time loading and loading, thus slowing your site down. Which defeats the purpose. People will just leave and never see the Zemanta ads anyway.
Oh, and by the way, if it was "that easy" to make money off ads on your site, we'd all be rich. Oops! That's not so common is it? Seems to me that some real effort and work is involved to do that. A silly little ad plugin (alone) just won't make it happen lol.