Tim Bray:

"Historically, the difficulty of collecting metadata at source has been generally large enough to outweigh the (potentially huge) benefits from collecting it. But I for one am not ready to give up on this approach. There are, after all, domains where metadata is at the core of the business proposition, and the process works there. For examples, the editorial staff who produce the Wall Street Journal add metadata as they go along, identifying people, companies, stock ticker symbols, and so on."