It's voluntary and in the form of a game. As long as people aren't forced to participate then people who want to play the games will participate in the advertisement which could be part of the game itself.
For example, prior to the launch of the successful True Blood series, there was an alternate reality game advertising campaign. This sort of use case is good for Steemit because it grows the market for content producers and expands the pie. The people in the world who have money are going to want to spend it advertising their games, their films, their products, and if Steemians can opt-in then it's fine.
It's going to happen no matter what. We will see ice bucket challenges, we will see people wearing certain tshirts with logos, and we will see transmedia ARGs, and in my opinion as long as it remains fun and profitable it improves Steemit.