This sounds like Paul Krugman's thesis that the run on the (unregulated) shadow banking system was at the "core of what happened" to cause the crisis and if only it was regulated, the crisis wouldn't have happened.

A great writeup about this by someone a bit more credible than Krugman can be found at http://blogs.wsj.com/economics/2010/02/23/so-what-exactly-ca...

Written by Yale and Wharton Professor Gary Gorton, who has held positions at the Bank Of England, the Federal Reserve and the FDIC.