In order to get the Facebook feeds working with Sitefinity CMS, there are few configurations that need to be set and taken into consideration firstly.
Firstly there is a new property that was introduced in Sitefinity 6.1 called EnableDtdProcessing ( located under Settings -> Advanced - Publishing ) which needs to be set to true.
When it comes to configuring the actual feed, there is one more thing that needs to be changed - the URL for the feed that is being generated by Facebook.
For example, if you want to create a feed based on your Facebook Notifications, Facebook generates a URL like this:
However, in order for the feed to work with our current implementation, the format at the end needs to be changed to atom10, instead of rss20 (manually). This is because Facebook feeds are generating an <access:restriction> element, which is from a custom extension called Bloglines, specifically created for Facebook. The problem is that the SyndicationFeed is having issues with that element. However, Atomfeed is not affected, thus the problem can be easily resolved by turning enableDtdProcressing property and also changing the format parameter to atom10.