The GUID element of the RSS export should be a unique and persistent identifier of the object. Currently URLs are used, which is not persistent. The consequence is that when an object's name changes and the RSS is refreshed, an item that a user has read will show up again as "new". Remote ID or object ID could be used instead.

http://validator.w3.org/feed/docs/rss2.html#ltguidgtSubelementOfLtitemgt

The issue that introduced the current GUID:
http://issues.ez.no/12226

Steps to reproduce

• Create an RSS export of a site, check the XML. Note the GUID of an item.
• Rename and publish that item.
• Clear RSS cache and refresh the feed.
• Observe that the GUID of the item has changed (bug).