The out-of-home media industry has overcome some questionable perceptions on Madison Avenue thanks to its increasing digitization, but it’s probably still best served as a specialty practice at most advertising agencies, S4 Capital Executive Chairman Martin Sorrell said during an interview at the Digital Place-Based Advertising Association (DPAA)’s annual summit in New York City Tuesday.

“There was always a fundamental concern about the industry,” Sorrell said, alluding to some less-than-transparent trade practices among outdoor media suppliers and buyers, including the fact that out-of-home media buys were not rigorously tracked and sometimes didn’t even run.

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