On the surface tagging seems to offer a new paradigm of organising information, one that reduces the cost of entry and so enables a long tail of participation to emerge. I’ve come to realise that the cost isn’t removed, instead it’s displaced and possibly increased. Tagging bulldozes the cost of classification and piles it onto the price of discovery.
In my view the total cost of an information retrieval system is the cost of classification plus the cost of discovery. In the formal classification world you have a very small number of people incurring a high cost in order to reduce the costs incurred by a very large number of people. In contrast the tagging world has the unit costs reversed: it’s cheap to classify, expensive to find. But the numbers of people involved are large in both cases so you end up with a lot of people paying a tiny cost to classify added to a lot of people paying a high price to discover. I think it’s pretty likely that the total cost is going to end up much higher than in the classification scenario.
What’s the cost I’m talking about? It’s people’s time. Time spent searching for things that should be easy to find.