I'm the author of this article and I'd love to learn more about what you found in your research. You can reach me at craig dot silverman at buzzfeed.com.
In all cases Google basically said it takes action against specific apps found violating policy. It seems unwilling to take action against a developer as a whole and ban them. I would also add that I suspect the Play store is not equipped to enforce a ban. People can easily create a newco and get back into the store. This is definitely a much larger issue. So I think that among other things these stories show that you can be a clear bad actor and still do business in the Play store.
Hi! I'm the author of the story and want to note that I only asked Google why it wasn't removing the apps after their investigation confirmed a major policy infraction. By then their investigation was close to a week old.
Google confirmed that these apps were committing ad fraud, and told me that ad fraud is against Play store policy. Yet the company was going to keep the apps in the store. That didn't make sense to me. Fortunately, they reversed their position.
(Also, in case it matters, I didn't submit my story here. But I always appreciate the interesting threads on my ad fraud stories.)