First, I would second using Open Calais if your content is well written prose. If not, it won't give you very relevant information.
There are a lot of ways to do multi-author blogs. Taxonomy is one way with each blog being a different taxonomy. You can't, also, use a CCK select list for this.
Even though CCK is one of the features that drew me to Drupal (having been a fan of John VanDyk's efforts with the Metadata plugin for Userland Manila), I haven't used it. The same is true for Views. I have to change that at some point, but I haven't needed to learn them yet for my own Drupal sites.
I'm not sure that you'd need a different content type for a multi-user blog, though, if I understand things correctly. You could use the core story module and taxonomy to get a multi-user blog. My cursory knowledge of Views leads me to believe that you could construct a view of the story content type with the right taxonomy terms and present that as a blog. Or, you should be able to forgo Views altogether — I'm well aware that you can have a listing of stories that have specific taxonomy terms associated with them right out-of-the-box with Drupal. (You can even have combinations of taxonomy terms in this listing — joining them with AND and OR.)
The stumbling blocks I see to this technique are:
I’m wondering, based on the Drupal Church Recipes Webcast, if there were ideas for using taxonomy more effectively. It sometimes seems overlooked — and at some points in Drupal’s past, overused — but it’s one of the features that lead me to Drupal in the first place.
In particular, I was thinking about its use to provide various multi-author blogs, such as for groups or committees, on a church site. One stumbling block I’ve come across is not knowing how to make an individual poster’s article get tagged with a particular taxonomy term — at least by default. I thought about trying to use Actions/Workflow or Workflow-NG/Rules modules for that purpose, but I’m not sure how it would play out.
It seems that taxonomy could play an important role. I’m reminded of the MuddyRiverMedia.org site, which I believe uses taxonomy heavily. On a slightly different tack, I have also been thinking about the OpenCalais integration you can get in Drupal now for automatically categorizing posts.