Google issue with feeds

http://www.google.com/webmasters/bot.html#noindextags

robots.txt is a standard document that can tell Googlebot not to download some or all information from your web server. The format of the robots.txt file is specified in the Robot Exclusion Standard. For detailed instructions about how to prevent Googlebot from crawling all or part of your site, please refer to our Removals page. Remember, changes to your server’s robots.txt file won’t be immediately reflected in Google; they’ll be discovered and propagate when Googlebot next crawls your site.

http://www.robotstxt.org/wc/faq.html