WASHINGTON, Dec. 16 - Fannie Mae, the housing-finance giant, for years has fended off critics who contend that the company is too big, too powerful and too risky. But the Securities and Exchange Commission's Wednesday ruling, that Fannie Mae had seriously breached accounting rules, could touch off a chain reaction that results in stricter government controls, legislation limiting its growth and possibly even a change in top management. Democratic and Republican lawmakers alike demanded on Thursday that senior executives, including the chief executive, Franklin D. Raines, return tens of millions of dollars in bonuses and other compensation that they had...