With LiveQuery you can establish "match" handlers to fire off when a matching object comes into existence, and when it goes out of existence. You can also establish event handlers on element that don't exist yet!
This is perfect for an Ajax environment where elements are popping in and out right and left. You can establish all your behavior up-front, and not have to worry about it later! [ September 18, 2008: Message edited by: Bear Bibeault ]