Stephen Downs Thinks the Semantic Web Will Fail
Some thoughts on why the semantic web might never become a reality. Main point: companies don't like to play nice with each other.
Update - I stumbled across Cory Doctorow's rather old (from 2001 it looks like) meta data article which is also a good read and still pretty accurate even today. Though some people are getting better with the use of services like Del.icio.us and Flickr. My favorite line:
Short of breaking fingers or sending out squads of vengeful info-ninjas to add metadata to the average user's files, we're never gonna get there.