This article on Metacrap is a quick and dirty reasoning about why this renewed talk about the "Semantic web" is a load of, well, metacrap. It's a business, people, and all they want to do is sell you something. If this brilliant idea were remotely achievable, it would have happened already. There are no tools we don't have that are fundamentally stopping a world of meta-meaningfulness.
I'm looking at you, tech writers. Content management is all about metadata. This is a must read for every tech writer, even you crotchety ones.
2.3 People are stupid
Even when there's a positive benefit to creating good metadata, people steadfastly refuse to exercise care and diligence in their metadata creation.
Take eBay: every seller there has a damned good reason for double-checking their listings for typos and misspellings. Try searching for "plam" on eBay. Right now, that turns up nine typoed listings for "Plam Pilots." Misspelled listings don't show up in correctly-spelled searches and hence garner fewer bids and lower sale-prices. You can almost always get a bargain on a Plam Pilot at eBay.
The fine (and gross) points of literacy -- spelling, punctuation, grammar -- elude the vast majority of the Internet's users. To believe that J. Random Users will suddenly and en masse learn to spell and punctuate -- let alone accurately categorize their information according to whatever hierarchy they're supposed to be using -- is self-delusion of the first water.