In 2002 I did a little experiment. With a little help from Dave Winer I generated a Visio VDX file from OPML. It was pretty straight forward. The idea at the time was to create a web service that could create a pretty picture of your connections to other weblogs and crawl those connections to create, you guessed it, a graph representing all your connections. Obviously I never finished it.
The reason I mention it is Facebook has done it, but it’s behind closed doors. It’s a Facebook thing. This is something the entire web could benefit from. What would it take for someone to create Open Graph as an open standard for showing relationships between sites? Facebook has an Open Graph spec. How can that be opened up?