The document discusses Google OpenSocial, which provides common APIs for social network platforms to allow applications to work across different social networks. It introduces OpenSocial containers as social networks that host OpenSocial applications. The "Dark Side of the Moon" refers to the ability of any website, not just social networks, to host OpenSocial applications by implementing the Service Provider Interface to connect to the website's backend. The document provides examples of OpenSocial reference implementations and recommends websites test hosting OpenSocial applications to potentially benefit from more engagement.