Lawsuits Besiege Fannie Mae on Accounting  NEW YORK (Reuters) - Fannie Mae &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=FNM.N target=/stocks/quickinfo/fullquote"&gt;FNM.N&lt;/A&gt;, under fire from  regulators, is facing a groundswell of lawsuits from  class-action specialists for billions of dollars in stock  losses stemming from the company's faulty accounting.