Once again David talks about tags:

When does ontological organization work? When you don’t have a lot of stuff, it’s stable, things have clear edges, an authoritative source and trained users. I.e., the opposite of the Web.

People have assumed that tags that mean the same thing are actually the same, but (Clay says) “movie” people don’t want to hang out with “cinema” people, and “queer” people certainly don’t want to hang out with “homosexual” people. There is information in the differences that thesauruses and categorization schemes miss.

And Clay moderates a panel on folksonomies here.