In a move that surprised the industry Wednesday, the Financial Industry Regulatory Authority’s head of enforcement, Susan Merrill, announced to her employees that she would step down.

A lack of details about when she plans on leaving and where she will head next has left the Street speculating, with some wondering how much she knows about the regulator’s track record of missing key abuses, such as Bernard Madoff’s Ponzi scheme, which rattled financial markets.

Merrill has headed up the enforcement division over the last three years, during which time FINRA was criticized for its lack of enforcement.

The regulator's website revealed that in 2007, the year Merrill joined FINRA, the number of enforcement actions that were brought decreased 2.2% to 1,177 from a year earlier. In 2008 that number slid even further to 1,073, although it increased last year to 1,158 as pressure mounted on the agency to increase oversight.

Merrill, 53, was hired at FINRA by then-chief Mary Schapiro, who now runs the Securities and Exchange Commission. In 2008, Merrill earned over $1 million, a year that the regulatory agency lost $696.3 million.

At an industry gathering last year, Merrill emphasized that FINRA would be toughening up this year with a myriad of new enforcement priorities. Her concern was that the push for regulatory reform would distract firms from complying with FINRA’s existing rules.