[roc]

As well as advertising networks and referral schemes.

Though, oddly, they've been late to the game on social.

[keypusher]

Scariest button on a porn site is the Like/G+ button.

[wisty]

Social took off when Zuck tricked users into giving out their real names, when meant social networks grew much faster (as old school friends would connect).

Porn does "social", but only anonymous social, which is naturally handicapped.

If someone created a social network which allowed better privacy controls, the porn sites would love it.

[dchuk]

porn is invariably a "solo" endeavor 99.9% of the time

[roc]

And yet a significant amount of money is being made by services whose natural market maps directly onto the porn site viewing market.

reviews, 'discreet' dating sites, sugar-daddy match-making sites, etc.