In addition to its problems with federal regulators, Fannie Mae is now facing at least four separate lawsuits filed on behalf of the embattled company’s shareholders by some of the country’s most prominent class action lawyers. “The scandal at Fannie Mae combines the worst aspects of Washington politics and Wall Street financial and accounting practices,” said Peter Seidman, an attorney at Milberg Weiss Bershad & Shulman, one of the firms that has filed suit. Seidman…