I just think of the fun spyware and rougue advertisers would have with the ability to do anything to the back button. I love the concept of AJAX, but the back button thing is a big problem. I'm not sure if giving developers the option to disable it is the correct way of overcoming the problem because of potential security issues. This one needs some thought, but my suggestion would be a seperate style window, opened by a 'A href="" target="AJAXWINDOW"' type link that browsers such as Firefox 2.0 and IE7 would know how to open. This special AJAX window would have security features built in, but enable closing the application but nothing else.

Good article nonetheless.