The GSEs have seen their share of the mortgage market continue to sag in 2005, but Fannie Mae and Freddie Mac will have to be careful about pursuing more unorthodox and potentially riskier loans that have flooded the marketplace. Data gathered by Inside The GSEs show the enterprises logged a historically low 27 percent share of total originations during the first quarter of 2005. Fannie notched $96.3 billion in new business during the first three…