Syndicate, another IDG event, is happening at the same hotel on the same days. I had some time before my talk on digital identity, so I snuck up to the third floor to heard Dave Weinberger talk about tagging, a subject that near to my heart lately.
What's the big fuss about? After all, aren't tags just keywords and metadata? Sure, but they're metadata written in ordinary language without a special vocabulary and are (usually) applied by the reader, rather than the writer. For some reason, people are more willing to tag other people's work than they are their own. Because this happens in public, there are social effects.
Without tags, Flickr is just another place to stick photos. Tags are what made it different. If you're doing research, tags represent a stream of social interest. Dave uses the example that he's doing research on taxonomy. By subscribing to that tag at Del.icio.us, he gets other people to do his research for him.
Tags don't always give us everything we need. If you go to Flickr and search for pictures of London and miss a few because they were tagged differently (say with "picadily")--no big deal. But if you're a brain surgeon or a planning a trans-atlantic flight, missing some data could be deadly.
Tag intersections can help solve this problem and some sites (like Flickr) are getting really good at this. Tag clusters help users navigate dissimilar items with similar tags. For example, if you look at things tagged with capri, you can see them clustered by tags intersections.
The basic message of tagging is that we can't pre-define them--they are user generated and flexible. This is why tagging works where taxonomies don't. People tag for themselves in a selfish way. The social benefits follow from this selfish behavior.
Dave brings up Quicken documentation and how lousy it is (they're not alone--just a convenience example). How much better would it be if users could tag it and help other users see it organized in a variety of different ways?