As RSS becomes increasingly popular, advertisers are considering putting ads in the feeds.
This is a poor move. RSS is a method of driving traffic (and advertising dollars) to a website. RSS feeds contain only the title and a short blurb for a article; you have to clickthrough to read the article.
But, when you embed ads in the RSS feed, you reduce the value of that feed and reduce its ability to drive traffic to your site. Any small advertising revenue you make from the RSS ads will be swamped by the ad revenue lost from reducing traffic to your site.