You went from "I have not heard of a case ..." to mentioning a few cases. I took your first comment at face value; now I don't know what to make of it.
Philandering around the workplace is usually a big no-no but it is definitely not corruption by any stretch of the imagination. I did this to show you that journalists will easily turn on their own kind.
As for the case of the government covertly starting a newspaper, I have not heard about it (but read about it in history books). They did this with the express purpose to change public opinion - since the current English newspapers were too critical of the government (with good reason). That really is before my time (20+ years or more).
I do not recall a single instance in my country where journalists were found guilty of corruption. Yet for politicians the list of the non-corrupt would probably be shorter.