I was thinking about the same thing... There's a theme called Squible (http://www.squible.com/squible/) by Theron Parlan and James Carppe that looks like it would provide full tagging utility. I am planning a site that will be very tag-dependent in its structure - trying to decide whether to incorporate Freetag or use Squible... would appreciate any suggestions that people have.
Basically, the idea is a medical information site - open to the public, to post links/descriptions to articles related to health and medicine - I'd like for readers to be able to tag their own and others' posts - so that site content can be viewed either according to a traditional disease classification (i.e. cardiac disease, lung disease, etc.) or more phenomenologically, via tags (i.e. "kid with fever" or "hallucinations" or whatever tags people devise that relate to their own health questions/experience.
So... what's the best framework for a site like this?