Mimicry and détournement allowed post-’68 protest culture to hijack the power of mainstream media along parallel channels, such as zines, fliers, and Persiflage (see displays at left). But they could also be employed in more direct assaults by momentarily seizing spaces occupied by the marketing industry itself. Inspired by the Situationists, prankster activists Ken Knabb and Ron Rothbart attached speech balloons, such as the one at right, to advertising posters around Berkeley in the wake of May ’68. The photos at right illustrate various techniques employed by British feminists attacking White Horse Whiskey billboards in 1982. Like Persiflage, the tactic of commandeering mainstream media space has been adopted and adapted in the digital age, where it has come to be known as tactical media. “Tactical Media are what happens when the cheap ‘do it yourself ’ media, made possible by the revolution in consumer electronics and expanded forms of distribution . . . are exploited by groups and...