The dramatic expansion of financial regulation approved by Congress this week bears the stamp of no one more than Treasury Secretary Timothy Geithner and gives him vast powers to determine the final form of the new rules. Half a year after some pundits were predicting he would be booted from the Obama administration for poor performance, Geithner is poised to inherit authority to shape bank regulations, financial market oversight and a new consumer protection agency. Few treasury secretaries have ever had such sweeping influence over such a wide realm.