My views on this have been pretty blunt. People do not want ads pushed to their phone. Obviously AdMob feels you do. But this person said it perfectly in the comments section of the article:
Not all marketers and brands feel being pushy is a good for business. But for Ad Server Networks it is their lifeblood. And they will do everything they can to convince clients this is a good thing. Opt-In advertising is the way to go. If people have their small phone screens cluttered with served Ads they will leave mobile web.