Look at how hard it is to get traction on investigations into the current foreclosure/securitization boondoggle - it's taken 3 years for judges to actually start looking, the federal regulators are completely uninterested, and maybe 4 state AGs out of 50 have even started looking. And these are obvious and clearcut violations of pretty straightforward laws. Their reputations and legal teams have been a buffer against all sorts of suits and investigations.

A Hollywood investigation would be worse politics, since you've have every TV station screaming about the government intrusion in investigating their parent companies. Look at things like the just failed Attorney General settlement with the banks - the worst case here is the company makes a one-time payment of a few pennies on every dollar of profit to some fund nominally targeted towards the victims. Then you throw in all the indemnification offered by corporate structuring and the fact that there probably aren't technical violations of the law here and good luck selling some accounting irregularities as a prosecution.

Maybe in a few years that stuff will change, but right now the environment is such that nobody really buys the idea of government actually smacking someone with TR's Big Stick.