"Mob indexing" has been used to describe the user- tagging phenomenon. It brings to mind an angry mob tagging products and sites. Tags might even become a customer satisfaction index. Customers who are unhappy with a company's product could submit links to a site and product pages with tags such as "poor service," "bad attitude," and so on. Unstructured user feedback would become easier. Links would show up in interesting, and perhaps unwanted, contexts. Will people take the time to tag links and content? Some will. But most? Tags' success will depend on whether and how people apply them, and whether enough context can be provided to make them generally useful. Applications that use tags are still on the fringes of the Web. Yet, tagging is gaining some acceptance and momentum. If it reaches critical mass, a whole new application ecosystem could evolve, giving people more "crayons" with which to color the Web and providing new ways to find, associate, and organize an increasingly cluttered information space.