"must slowly evolve into adult portals or else they will die."
wrong, they already have.
"within the next 2 years, the hun, buffet, whoever, will no longer be simply offering extensive lists of free porn."
wrong, the lists will even get bigger, more links to free movies will follow ... only difference will be that more and more links will link to gallerys belonging to the owner itself ...
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Don't innovate - imitate!
... giving away
mass traffic for free !!