Microcontent is modular content. Each item of microcontent is an unique, individually addressible chunk of content defined by metadata focused around a particular idea or small set of related ideas.
Macrocontent is any collection of organized microcontent objects that form a publication. A weblog is actually “macrocontent” — it is a published, temporally organized collection of microcontent objects that comprise its individual “postings.” A wiki could also be seen as macrocontent — it is a published, topically organized collection of microcontent objects comprising its wiki-nodes. At a certian point in the near future I think that even common Web pages will become macrocontent — that is they will be comprised of numerous microcontent objects arranged in a particular order on the page. By constructing Web pages and Web sites out of modular units of microcontent sites will become far more useable and searchable. Furthermore, each microcontent object on the page will become a node that others can subscribe to, comment on, link to, etc. Weblogs are just the first use of microcontent — I think that in fact the microcontent paradigm will become a key element of next-generation Web publishing, and even of the desktop. When content becomes granularized into modular, semantically rich components publishing systems, publications and reading/browsing tools can all benefit from improved precision, content management and interaction capabilities.