Google could easily do more; at least they could rigorously check ads for the most popular open source programs, the ones that are downloaded the most, and they

Google could easily do more; at least they could rigorously check ads for the most popular open source programs, the ones that are downloaded the most, and they could make sure that official sites for popular programs rank highly. If that costs them some revenue, it's going be a small hit, the scammers aren't giving Google that much money.