During my excessive search for real world usage of microformats I stumbled across the rubhub. This is a search engine for relationships between websites and indirectly for relationships between people based on the XFN standard. XFN is widely supported and offers the possibility to transfer simply social relationships to existing websites.
The rubhub is quite simple, a search form takes any part of search request and all fitting websites will be listed. If you find an interesting website, click on it for further details and a more complex listing about relationships is shown, it contains outgoing, incoming and reciprocal contact classification. Although its quite slow, it would be a great idea for a new social networking extension for existing great player such as openbc. Nevertheless, the way of visualization may be extended in upcoming versions.
The interesting aspect on this simple approach is that new global market ways may be established this way. Think about a scenario when a book seller tries to find a really old rarity. The only antique dealer he know does not offer the desired book, but this antique dealer also holds a list of well known friends on his website. Those friends are related to his work also antique dealer and after some indirections the initial book seller potentially finds the desired book at a friend of a friend’s website – happy end 🙂