for people who are registerd with godaddy.com, they give a very simple and free tool to point any website to any domain name... e.g if you buy a domain name wazoo.com you can go to the control panel of godaddy and point it to yahoo.com by writing it in the given text area and then click "ok" ..its that simple.. it only takes 24 hours to complete the request and the result would be exactly the same as described by SUPERSEO. Anyhing indexed by search engines would look like
www.wazoo.com/members/profile..blah blah (the original would be
www.yahoo.com/members/profile..blah bhal)
Also i think go daddy has the option of editing the header information to the domain name.