The tussle between Fannie Mae and the Office of Federal Housing Enterprise Oversight over allegations of accounting abuse not only threatens to blow the roof off the GSE arena, but could also cause a significant shakeup in the accounting industry itself. Deloitte & Touche, one of the four remaining major accounting firms, was hired by OFHEO in February to help assess whether Fannie’s accounting procedures were up to par, and the agency subsequently released a…