CANNES — According to GroupM Chairman Irwin Gotlieb, many media reviews are happening at least in part because of a bad habit agencies have developed of promising too much.

“Everything comes home to roost eventually,” says Gotlieb in an interview with BeetTV at Cannes this week. “Those who over-promise massively and fail to deliver have seen their clients suffer market share loss. When a client suffers market share loss, there’s going to be a review.”

Gotlieb also observes that addressable TV is quickly becoming a scalable proposition, with Dish and DirecTV now fully equipped for addressability and other cable providers building out their capabilities. He also notes that GroupM’s advanced TV business unit Modi Media now has a billings run rate of $125 million, up from nothing 15 months ago when it started.

He notes that addressable TV is still supply-constrained, since it’s been limited to the two minutes of ad space owned by the cable operator, but he expects that to change.

“There’s no question that the major broadcasters and cable networks will participate, and they will make their inventory available,” he says. “That’s where the huge opportunity exists, and it will be transformative to the media.”

We interviewed Gotlieb as part of a series on video advertising at Cannes Lions, presented by true[X]. For more videos from the series, please visit this page.