2011 rule changes - shortened shark fins 03 February 2011
Teams are no longer able to connect engine cover extensions (commonly known as 'shark fins') to the rear wing. This is related to the ban on F-ducts - in 2010 many designers used the connection to form an airflow channel for the duct. It's possible some teams may persevere with reduced shark fins, which also give some benefit in terms of stabilising airflow to the rear wing (as well as providing additional advertising space for sponsors).
FIA Technical Regulation
3.9.1 - No bodywork situated between 50mm and 330mm forward of the rear wheel centre line may be more than 730mm above the reference plane.