Joi explains his interest in micro-content
It's a good summary, but it misses a key point. By emphasising the difference between commercially produced 'content' and user-created 'micro-content' he is ignoring the enormous area inbetween.
The current content publishing model is only efficient for large-runs of sales - sell under a few thousand books, a few hundred thousand CDs, or a few million cinema seats, and you won't be welcome in commercial publishing.
This gap is gradually being bridged by innovative companies, such as Cafepress and Customflix, but both of these are still creating physical goods.
I think there is a huge opportunity here to be the eBay of digital media, and I think mediAgora is the way to go about it.