Forget too big to fail. In the eyes of federal regulators, many Wall Street firms are too big to punish. During the past three years, some of the nation's largest financial firms have been accused by the government of cheating or misleading clients and ripping off tens of thousands of consumers of their investments. Despite these findings, these financial giants got, sometimes repeatedly, special exemptions from the Securities and Exchange Commission that have saved them from a regulatory death penalty that could have decimated their lucrative mutual fund businesses. Among the more than a dozen firms that have gotten these SEC get-out-of-jail cards since January 2007 are some of Wall Street's biggest, including Bank of America, Citigroup and American International Group. SEC rules permit corporate lawbreakers to apply for what are known as Section 9(c) waivers from one of the agency's harshest penalties - effectively shuttering the violator's mutual fund operations - but regulators never rejected any of these firms' applications. In fact, the last time the SEC's staff could recall a waiver being turned down was 1978. The SEC declined to comment in detail.