As we said, Google is not sneaking this feature in involuntarily, as some feared Microsoft would do. It works only for those who want it. First, you have to download and install the Google toolbar on your computer, a totally voluntary action. Listings cannot become links for you if you do not have the Google toolbar installed. If you do, you will then have an option called "AutoLink." AutoLink enables you to turn several things into links: street addresses, motor vehicle VIN numbers, and book ISBN numbers. We should point out that Google cannot turn book titles into links, at least not yet. It can only convert ISBN numbers to links.

Next, you get to decide whether you even want to use this feature. It is totally voluntary. You can have the Google toolbar but still leave AutoLink disabled. If you don't use it, Google will never convert ISBN numbers it finds on websites to links. If you do activate this feature, Google will enable ISBN numbers on websites to become links. Whereto, you might ask. The default answer is a name well known to us all: Amazon! If AutoLink is activated, ISBN numbers on others' websites, perhaps your own, become links to for sale listings on Amazon. Surely this is not what you intended, but Google enables your customer to convert ISBN numbers on your website to links to Amazon listings.

The customer can choose to change those ISBN links to links to four sites other than Amazon if they prefer. They can link to the relatively harmless WorldCat library listings, Barnes and Noble, Booksense, or their own Froogle. If the customer changes the default from Amazon to, say, WorldCat, then the ISBN numbers on your site will become links to WorldCat instead of Amazon. My guess is that most people will leave the setting on Amazon, but that is only my guess.

Now, if the ISBN number in your listing is already a link, AutoLink will not override it. That link will still redirect the visitor to the intended page. AutoLink will only convert ISBN numbers that are plain text, not links already, to links to Amazon or another chosen site.

So let's go to a couple of Amazon's competitors to see what happens. First I went to Abebooks, which recently added ISBN numbers to their listings as part of a group of changes that have not entirely pleased all of their booksellers. AutoLink might have caused those booksellers even more consternation, since those ISBN numbers are now displayed right next to the titles in Abe listings. However, the Abe sellers were saved by the fact that the ISBN numbers on Abe are also links to the detailed descriptions. As noted above, AutoLink does not override existing links. Clicking on the Abe ISBN's takes you to the Abe details, not Amazon. However, when I looked up "Tom Sawyer," I found one dealer who also included the ISBN number in the basic description. Since this ISBN was not a link to the detailed description, Google highlighted it for me, and when I clicked the ISBN number, it took me to Amazon's site. The dealer wanted $1 for his copy, while Amazon offered copies as low as $.01.