Tag Soup
Clay Shirky on tagsonomy: tags are cheap reader (not author/editor)
supplied metadata, having (at least) these characteristics:
1. It’s made by someone else
2. Its creation requires very few learned rules
3. It’s produced out of self-interest (Corrolary: it is guilt-free)
4. Its value grows with aggregation
5. It does not break when there is incomplete or degenerate data
And this is what’s special about tagging. Lots of people tag links on
del.icio.us.