Outdoor ads have “become a social channel,” as more passersby post pictures to social media. Nielsen found that about 25% of U.S. adults have posted a pic of an outdoor ad to social media. Case in point: Spotify’s takeover of an NYC subway station with David Bowie images, which organically reached over 50 million social media users. The trick to getting people to engage with the old school ads? One ad agency exec explains that marketers “need to think of [outdoor advertising] more as an art installation than an ad.” (Fast Company)