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. (Wired News, 12/09/04.)
Related: My post, BLOGSNOB SIMPLEAD EXCHANGE.