It`s an existing idea they`re catching onto and adding some flavor.
A fair number of eastern-made free to play mmos have been doing it for maybe 2 years. What happens is if u need to do something ingame that has a cool-down, something like ur minimap will turn into an advert.
Crossing zones is a favorite one, as they show some ads and have linkage. Once u finish messing about with the ad, the game continues.
9Dragons has some such ads, many of them were korean when I played it 23/6.
Be interesting to see google`s approach in the wild.