Think about it. You could post diary entries, articles, replies, URLs, messages to individuals, certifications and messages to mailing lists via e-mail. One neat side-effect of this would be the ability to use PGP/GPG for post authentication.
Take a look at lkcl's demo site, or the Open-IT site (which uses lkcl's mod_virgule) for an idea of what could be done with the Advogato model. Pay close attention to the concept of interest certifications and searching based on a seed person's certifications. Very cool.
Now imagine applying this model to mailing lists as well. One could certify threads/messages as 'Intriguing' or 'Fascinating', one could annotate useful threads/messages, much as one can annotate URLs. One could search using a seed person's cert metrics as a search term.