The nature of fandom seems to have morphed in the past decade. In the old days of sci-fi conventions and Bobby Sherman fan clubs, fandom was a subculture reserved for the very young or the very obsessed—or, in the case of the Grateful Dead, the very stoned. As fantasy and comic-book franchises have taken over the entertainment industry, nerd culture has become mainstream. Now that couch potatoes have social media, they have risen up and become active, opinionated participants. As a result, movie studios and TV showrunners have to cater to subsets of diehard devotees, who expect to have a say in how their favorite properties are handled.