Right, the point is that if HotOrNot started out as a dating service, they wouldn't have gotten any users at all. People join a dating site to find other users to date - they only find other users to date if the site already has users. So you end up with a chicken-and-egg problem where everybody is waiting for everybody else to join. I'm curious how other dating sites have solved this - my guess is that they either tapped a large network of friends or they recruited users from an existing singles community.
HotOrNot actually faced a terrific scaling battle anyway: http://www.webtechniques.com/archives/2001/05/hong/. They got far more users by starting as a rating site than a dating site.