Amazon has introduced a new feature that promises to be more useful than the Statistically Improbable Phrases feature that launched a few months ago. The “SIP” feature finds distinctive phrases inside books and then linked users to other books that contained those same distinctive phrases. For example, Stephen Greenblatt’s Will in the World contains five instances of the distinctive phrase “deer poaching,” which Amazon tells us also appears in several other books, including Deer and Deer Hunting Book 2: Strategies and Tactics for the Advanced Hunter. Amusing, but not terribly useful. Amazon’s new feature, Capitalized Phrases” or “CAPs,” links books by proper names and places, so by clicking on “King Lear” from among the CAPs for Will in the World, you get a list of books that mention “King Lear.” This seems like a potentially very useful research tool – especially if Amazon decides not to limit the results to twenty or so books as they are currently doing. These “phrases” features by Amazon also represent a foray into the relatively new Internet phenomenon of tagging, which sites like del.icio.us use to categorize Web sites. Since the process is external – in the case of del.icio.us, the tags are applied by users – and has a human element to it, sites that employ tagging have the potential to be “smarter” than those that rely on old-fashioned search engines. It will be interesting to see if Amazon begins to allow user submitted tags in addition to its Search Inside a Book data to create a deep and highly intuitive way of organizing its massive inventory.