I think the YTMND guy put it best when he realized that all of the top content on his site is adaptations (to put it nicely) of content created elsewhere. None

I think the YTMND guy put it best when he realized that all of the top content on his site is adaptations (to put it nicely) of content created elsewhere. None totally original. So that's about 99.99999% vs 0.000001%. So beware of creating a site where users have to create totally original content. Sites like hacker news have it easy in that respect.