Don Park outlines an interesting potential solution to Google's proposed Auto Link feature of its Toolbar. Essentially his solution is to allow content author's to opt-in via tagging content for auto-linking.
The question I have about this is if you're going to go to all the trouble to mark up your content in this way, why not just provide the link yourself? One benefit I do see is in the case of an ISBN number. As a content producer, I might link to Amazon. However, if my user has an account at BookPool, she might configure the auto-link toolbar to link ISBNs to that site instead.
Of course, in general, I might not want that since I'd prefer to get credit for links to Amazon. But that's beside the point. If I opt in, it's the potential to give users more control. This assumes that Google gives user that level of control.
Another question I have is if content authors start using this tag, what stops browsers from adding AutoLink to pages that opt-in? In effect, Don's suggestion creates an extension to HTML and by being opt-in, anybody should be able to hook into that, not just Google.
I'm not sure Google would want to go that route. Microsoft had its hand slapped by attempting an auto-link. Google perhaps thinks it can squeeze by since it's not a monopoly power on the desktop and it promises to "do no evil". But by making AutoLink opt-in, that should in theory make it palatable for browsers such as IE and FireFox add that feature.
Ultimately, I think AutoLink would be a great feature if it was controlled by the users. A user could control links to addresses so that they go to his or her favorite mapping site and an ISBN would link to the user's favorite bookseller.