On Thursday, Warren released two highly provocative letters demanding some explanations. One is to DOJ Inspector General Michael Horowitz, requesting a review of how federal law enforcement managed to whiff on all 11 substantive criminal referrals submitted by the Financial Crisis Inquiry Commission (FCIC), a panel set up to examine the causes of the 2008 meltdown.

The other is to FBI Director James Comey, asking him to release all FBI investigations and deliberations related to those referrals. The FBI typically doesn't release investigative details about cases that the DOJ chooses not to pursue, but Warren pointed out that in releasing information about presidential candidate Hillary Clinton's use of a private email server in July, Comey had pretty much shattered that precedent and set a new one.

"You explained these actions by noting your view that 'the American people deserve those details in a case of intense public interest,'" Warren wrote to Comey. "If Secretary Clinton's email server was of sufficient 'interest' to establish a new FBI standard of transparency, then surely the criminal prosecution of those responsible for the 2008 financial crisis should be subject to the same level of transparency."