I am talking about Amazon's decision to add a folksonomy-based categorization scheme to the vast online store. Next time you search for a book on Amazon's Web site, pay attention to the little Your tags box on the details page. The online merchant describes the new feature like this:"Tags provide an easy way for you to remember and classify any item on the Amazon site for later recall. For example, you might be shopping for holiday gifts and tag items with the names of the people on your shopping list. You might also want to tag items you've purchased in the past. Don't like the way Amazon has organized its science fiction or cookbooks? Tag the items you care about with the categories that matter to you. Because people's tags are visible to others, a great side effect of tagging is that you can navigate among items through other people's tags. What items have people tagged "gift" or "Tuscany" or "robot?""It's the last example — other people's ability to see your tags and yours to see theirs — that makes this type of categorization potentially very powerful.
I have written about folksonomy before, explaining that the method has grown organically out of a need to complement burdensome formal classification efforts done by site owners with more casual categorization by users and their keywords. Folksonomies are particularly useful when the amount of items to classify is very large. It increases a user's chances of finding an interesting item by browsing.
Note! The cherry on top is the suggestive AJAX search Amazon implemented in the Your tags box. As you begin to type, tags added by other people are displayed as suggestions. Nnnnice.