It was inevitable that the collapse of the $300 billion auction-rate securities market in 2008 would trigger securities litigation. But the ARS freeze also spawned a massive antitrust case, after a trio of plaintiffs firms cooked up a theory that the market's demise was triggered by an illegal boycott on the part of major banks.

Class action litigation is beginning to take shape over allegations that major banks manipulated Libor, the benchmark rate used to calculate interest on trillions of dollars in securities globally. On Monday the federal district court judge hearing the litigation consolidated 20 class complaints, and appointed interim class counsel.