I think it would be interesting to optionally expose the list of favorited urls as a feed (rss and/or json) that could be consumed by external applications. E.g. maybe someone else wants to to follow your favorites as an rss feed, or you want to build a link blog in a personal website using the json endpoint as a data input. A somewhat related feature would be to publish your list of followed sites as an OPML + json endpoint.

I haven't figured out the right approach to this (thoughts appreciated!), but some ideas I had:

• marking some feeds with a private flag (to be excluded from public feeds) and then adding a user config flag to explicitly enable the favorite feed endpoint.
• alternatively, always expose the endpoint but password or auth-token protect it.