Wall Street's worst nightmare is a heroine to consumer advocates. When has a Harvard professor of bankruptcy been the subject of an admiring rap video? Elizabeth Warren, who helped force a Bureau of Consumer Protection into the Finance Reform bill, was appointed today as a White House advisor. How much clout will she have in the future? Instead of heading up the new bureau, she will report to Treasury Secretary Tim Geithner, an occasional foe. Will she have the power to write tough rules for mortgages, credit cards and payday loans? Will she ever be asked to enforce them?