Useless Warrior - I think there is enough history for adult sites that there should be a field comparable to archaeology but strictly studying the origins of porno. Let's call it "pornology"?
The "pornological" origins of the current free site structural paradigm could best be fathomed from a thorough survey beginning with
www.archive.org
But someone else will have to do that because I'm just a pornographer and not a pornologist or pornological scientist.