The URL should be appliedrationality.org, not www.appliedrationality.org.
I agree (in the sense that this is what I do with my own sites), but here's a pro-www argument. (More accurately it's an argument against using a "bare" domain name in web addresses; that link itself does not start with "www.", but it does start with "faq.".)
The arguments are good, but as you say they do not support 'www' as opposed to any other prefix. 'www' should be consigned to the flames.
The new Center for Applied Rationality website has launched! We'll be adding content as time goes by. Let us know if you find broken links, etc.