sentences:  They became subject to the equivalent of a bank run in 2007 and 2008, in which investors (rather than depositors) withdrew sources of financing from the shadow system.This run became known as the subprime mortgage crisis.During 2008, the five largest U.S. investment banks either failed (Lehman Brothers), were bought out by other banks at fire-sale prices (Bear Stearns and Merrill Lynch) or were at risk of failure and obtained depository banking charters to obtain additional Federal Reserve support (Goldman Sachs and Morgan Stanley).