Google’s director of search quality bashes manual ontologies, with much justification.
However, his attempt to paint successful ontologies into a tiny niche doesn’t exactly work:
The best place where ontologies will work is when you have an oligarchy of consumers who can force the providers to play the game. Something like the auto parts industry, where the auto manufacturers can get together and say, “Everybody who wants to sell to us do this.” They can do that because there’s only a couple of them. In other industries, if there’s one major player, then they don’t want to play the game because they don’t want everybody else to catch up. And if there’s too many minor players, then it’s hard for them to get together.
Aren’t search engines and browsers in a sense oligopolistic (actually oligopsonistic) consumers of web content? There are only a few of each that matter anyway.
Barring interest from Google, Microsoft, Mozilla, and Yahoo! there may be oligopsonists (or monopsonists who want their standards adopted) in niches that can drive metadata adoption in their niches.