I was recently part of a forum discussion regarding utilizing subdomains when building a blog network. It is certainly an easy way to manage your network in that you won’t find yourself “ftp-ing” into a dozen different domains.
A point that I brought up during the topic was that About.com has been using subdomains for (probably) as long as they [About] have been around. No one could disagree that it was fairly easy to navigate About and find the topics that interest them.
With the recent introduction of Erati, I find the use of subdomains put to very good use. I wonder if we are starting to see a glimpse of things to come?