2011 rule changes - F-duct ban 03 February 2011
For 2011 the FIA have specifically outlawed the use of driver movement to control any system that influences the car's aerodynamic characteristics. This means no more F-ducts, where the driver covered a hole in the cockpit to alter the airflow to the rear wing, allowing it to stall and cut drag at high speeds.
FIA Technical Regulation
From 3.15 - Aerodynamic influence - With the exception of the parts necessary for the adjustment described in Article 3.18, any car system, device or procedure which uses, or is suspected of using, driver movement as a means of altering the aerodynamic characteristics of the car is prohibited.