I was just thinking it would be useful if there was a stream generated from activity such as adding a post to favorites. Also an aggregate of lots of different recent activity, for example earning a badge, selecting an answer, leaving a comment, etc.. this could be used for a personal website or social network then as a badge of activity.
Most of all the feed of the favorites would be great for me as more and more I find some things at SO such a great reference that I bookmark that thread, it would be sweet if I could have these import and use the feed in various ways.