While I agree with your point, it's not the point of the blog entry:
"...if it doesn't work when you've got one, it's extremely unlikely to work when you have dozens."
Also, there is no mention of the difficulty of gaining users, merely that your idea won't be any better when you've got them.
That's clearly not true in several cases.
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.