Of course, tagging has its drawbacks, and some Webophiles aren't quite convinced it will evolve into the Next Big Thing.
Consider classifications for a common pet.
'If one group decides we're going to call them 'canine,' another 'dog,' another 'puppies,' ... when someone goes to search for what they call the dog, they are not going to pick up everybody's tagged instances,' said Geneva Henry, executive director of the Digital Library Initiative at Rice University.
Engineers recognize the shortcomings and are working on better tools.
Search for 'automobiles' on Flickr, and you're given 'cars,' 'car' and 'porsche' as related options. Enough people tag photos both 'automobiles' and 'cars' that clustering software can tell they are related.
Another drawback lacks an easy solution, though. Once tagging takes off, marketers are bound to add irrelevant tags to hijack you to the latest Viagra ad.
Warns Danny Sullivan, editor of the online newsletter Search Engine Watch: 'The noise and deliberate manipulation will probably just bring the system into a crashing halt.'
CNN.com - 'Tagging' helps unclutter data - May 3, 2005: