Book addicts getting hooked on LibraryThing, tags

"Tagging" is the Internet buzzword of the day. It's the organizing principle behind Flickr, the wildly popular site where people upload and share photos. Instead of sticking pictures in folders labeled "2006 vacation," for instance, Flickr users assign "tags" to the photos -- informal keywords such as "beach" or "sand dunes" -- making them easy to find.

Tags are getting popular with book lovers too, and some libraries allow users to add tags to their card catalog. Leading the charge in book-tagging is LibraryThing, which has signed up nearly 50,000 users since it was launched last August. Members enter books they own, and assign tags as a way to organize them and compare their collections with other LibraryThing users.

Entering your personal library at LibraryThing is pretty easy, and addictive. And once you've done it, you'll see lots of interesting connections between your books and other members' collections.

Why is this important to booksellers? At the rate it's going, tags may become a popular way for readers to discover new books they want to buy -- especially the obscure, scarce books so profitable for online sellers.

If you're a regular reader of this blog, you've probably noticed the blue "tag cloud" on the right, which shows popular keyword searches here. If you want to see a huge one, check out the most popular tags assigned by LibraryThing users. In theory, this is -- or could become -- the most detailed and current, yet easy-to-use book index on the planet.

For the past six months, Amazon also has been allowing users to tag books, but the feature hasn't gotten much traction yet -- perhaps because it's so hard to notice the small "Tag this product" section on Amazon's doodad-filled product pages.

Meanwhile Amazon has been quietly working on something similar to LibraryThing, which it calls Media Library. This replaces what Amazon used to call its "Digital Locker," which served as a safe deposit box for e-books or downloadable movies you'd purchased previously from Amazon.

Now, all of the purchases you've made on Amazon -- including paper-bound books -- can be seen in Your Media Library. One weakness of Amazon's service is that only items you've purchased from Amazon can be added.

LibraryThing has been growing like wildfire, with virtually no marketing except word-of-mouth. Just recently the company's founder hired his first full-time employee (a librarian named Abby) after AbeBooks.com bought 40 percent of the site.

Basic accounts at LibraryThing are free, and limit you to 200 books in your library. You can upgrade to unlimited usage for $10 a year, or a one-time payment of $25.