Share and share alike

Ross defends the notion that viewing hard porn is somewhat equivalent to adultery. Julian Sanchez dissents. I want to know this: if you watch the porn together, are you both cheating? Or are you swinging? On a related note, the debate for some reason strongly reminds me of this: See web-only content:
http://www.theatlantic.com/business/archive/2008/06/share-and-share-alike/3700/

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http://www.theatlantic.com/business/archive/2008/06/share-and-share-alike/3700/