I guess it was inevitable. Ads are coming to RSS.
As soon as mainstream publishers incorporated RSS feeds into their web businesses, you knew that ideas on how to make money from them would inevitably follow. This almost always means advertising, the bane of readers' existence, but it's the reason most content on the net remains free for the asking. So while some may protest the idea of monetizing RSS, it's inevitable. The trick will be to make it as unobtrusive as possible.
Since traditional media companies move slowly when it comes to incorporating new ideas, the first ones to dip their toes into the commercial waters have been, not surprisingly, folks like Jason Calacanis, founder of Weblogs, the parent company of Engadget, a well-trafficked tech blog, and Nick Denton, founder of Gawker and Wonkette, both of which have incorporated ads into RSS.
I'm not sure this is a bad thing. The more targeted and relevant that advertising can become, the less I mind it. Sometimes I really am looking for certain products or services. I'm more than happy view ads of things I really might want if it means viewing less mass advertising that I find irrelevant.