folksonomy vs. taxonomy
There is an emerging scheme for classification of information on the web, largely driven by the public on some very popular community websites - that has become known as a folksonomy. A folksonomy is the polar opposite of a taxonomy as we know it and organises everything without hierarchy or discipline. It is classification by the people for the people. The idea is that any piece of information can be given 'tags' to classify it. Tags are just simple words to pigeonhole things. Furthermore, anyone, in theory, can tag anything.
A good example of this in action is the picture sharing site flickr - see http://www.flickr.com - if you have not seen this before do have a look, it is quite interesting.
The idea is that it should be easy for people to find items of interest. In practice though, it seems that as information accumulates it becomes increasingly difficult to find things again. Ah well, back to the drawing board. I think that Carl von Linné might be smiling down on us.
Further info: Wikipedia:folksonomy
note: Wikipedia is a very useful website if you are not familiar with this.