Can you give some examples?
> And how many press organizations will do that?
Not all papers - but some do. In my country there are 2 good English newspapers and one magazine that does excellent investigative reporting.
> More important, that's irrelevant because corruption investigations rarely involve lawsuits.
Corruption cases are full of lawsuits! My favourite investigative magazine (http://www.noseweek.co.za/) was closed for almost a year because the person running it was sued for libel. He won that lawsuit - but he had to stop publishing that year while defending himself in court.
In 2007 he was sued by a bank to prevent him from naming a list of clients that the bank helped with tax evasion - he won again and published the list of names.