This excellent piece by Mother Jones takes an in depth look on how 9000 reporters failed to report on the problems on Wall Street.  I'll simplify.

These reporters are hacks.  They are not reporters.  They are shills who repeat what the powers-to-be tell them to repeat.  In order to have their jobs, they are not allowed to be real reporters.  They work at the behest of the Wall Street executives they are supposed to report on.  If they dare report the truth they are out of jobs.

In exchange for being shills they get access to these Wall Street tycoons.  Instead of digging for stories, they get handed fluff pieces by public relation staffers and simply copy these fluff pieces for their stories.  It's an easy job being a shill.  You get nice lunches and dinner, a nice salary, all for being a liar masquerading as a reporter.

How could 9000 Business reporters not know a story that was right in front of their eyes for years and would have taken about 5 minutes of research to find?  Simple - They were being paid not to report the truth.