At NewsGator and Sepia Labs I worked with Brian Reischl, one of the server-side guys. Among other things, he worked on NewsGator’s RSS content service, which reads n million feeds once an hour.
(I don’t know if I can say what n is. It surprised me when I heard it. The system is still running, by the way.)
Brian is intimately acquainted with the different ways feeds can be screwed up. So he posted Stupid Feed Tricks on Google Docs.
I quote the entire thing below for people like me who don’t have Google accounts. The below is all by Brian:
He then goes on to list several dozen edge cases the feed reader had to handle.
Writing software is hard.