The only way to do that would be for a competitor to implement it and begin gaining traction because of it. Right now, the cost of the wrongfully terminated is less than the cost of wrongfully terminating them and probably always will be unless Google starts loosing people afraid of being wrongfully terminated. That number becomes much larger.

Want to incentivize Google? Convince Bing to implement it and see if Adsense customers convert as a result. If I felt Bing was treating their customers/vendors (ads is a really weird relationship :) better, I would consider using it (since as a search product it has approached Google pretty close).