Here are the slides from a stock talk I used when I was in the MIND Lab on the social and evolutionary underpinnings of play. "Why Play? The evolution of play as increasing complexity of brain, behavior, and environment" was first presented to an informal group at Michigan State University in 2005. The talk is a dialectical/synergistic response to the work of Peter Ohler, Rene Weber, and others.
Here are the slides from a stock talk (first presented in 2004) I used in the MIND Lab on the (statistical physics-flavored) theory behind Social Media. "From Networks to the Web: the complexity of massively parallel Human-Computer Interaction" is a bit dated in spots (e.g. somewhat pre-social media), but gets the point across.