rashmi writes a fantastic piece on why tagging works better than categorisation A cognitive analysis of tagging (or how the lower cognitive cost of tagging makes it popular)
At the start, let me confess that I struggled with this topic. From my first encounter with tagging (on systems such as del.icio.us & flickr), I could feel how easy it was to tag. But it took me a while to understand the cognitive processes at work. What follows is Rashmi’s theory of tagging – my hypothesis about the cognitive process that kicks into place when we tag an item, and how this differs than the process of categorizing. In doing so, my hope is to explain the increasing popularity of tagging, and offer some ideas regarding the design of tagging / categorization systems.
Read the article – it’s a very powerful concept, and rashmi captures it extremely well.