Google has published a set of best practices for publishers participating in the beta version of its AdSense for feeds:
- Syndicate the full text of your articles. The more content that is available in a site’s feed, the better the user experience and the more likely people are to subscribe to your feed. If you can’t put the full text of your articles in your feed, then in addition to the headline of each article, include as informative a snippet of the article’s text if possible.
- Don’t include more than one ad unit per article. Feeds represent an uncluttered, highly targeted medium, and these characteristics should be preserved to maintain and grow an audience.
- Place the ad unit at the end of articles. The content of an article is what users are most interested in, and that should be placed first. Then they can read the ad with more context.
- Include terms and conditions on the use of your feeds. Just as you have rights associated with the original content you create on your Web site, so do you have rights associated with your feed content. If you have concerns about those rights, specify the exact terms and conditions for the use of your feeds somewhere on your site.
Source: Google AdSense Support