Google has launched a clean-up operation to prevent raw RSS feeds from showing up in the search results. It’s a step that will be appreciated by both content publishers and search engine visitors alike.
To start with, Google has de-indexed all FeedBurner RSS feeds from their main web search index (see screenshot). Even RSS feeds that are syndicated via the FeedBurner MyBrand service (e.g. feeds.labnol.org/labnol) are no longer available in Google Search.
This is true for all feeds that exist on FeedBurner irrespective of the NOINDEX settings that you may have configured through the FeedBurner Dashboard.
Though the XML feeds of Blogger blogs (blogspot.com/feeds/posts/.. and blogger.com/feeds/..) are still indexed by Google, it should not surprise if blogspot feeds also face the Google axe just like FeedBurner feeds.
[Worth noting that both Blogger and FeedBurner are owned by Google.]
This is probably an excellent step from Google for two reasons - one, it solves (to some extent) the problem of duplicate content and two, when non-techie users click on search results that point to RSS feeds and not regular web pages, they may not know how to deal with them and quickly leave.
Related Reading: FeedBurner FAQ
Update from Matt: Google has been working to handle all feeds better (not just Feedburner feeds), namely by properly canonicalizing feeds to their corresponding HTML pages (as a related note, that also means we’re showing raw RSS feeds in our index much less often).