Honestly i think Google is partially to blame here as well. They can clearly see someone is impersonating the domain yet wants to throw money at it for an ad. I assumed they had filters against that sort of BS.
They are to blame.
They aren't check the links the person is using for their adsense service.
Which they should have a dedicated quality assurance department to look at these type of things from happening.
Alot of people use their search engine so they have the responsibility to look after their customers who view their site and use it for their searches.
Wouldn't you agree?