The active spoiler on the MINI Coupe creates down-force but also reduces turbulence behind the vehicle.  The larger front lip on the lower front bumper also creates down-force to increase stability.  Here are some behind-the-scene images and photos of the MINI Coupe undergoing wind tunnel testing.  A description from [translated into English]:

Take an exclusive look into the most advanced wind tunnel for automobile research and discover the exciting details of aerodynamics research in the MINI Coupe – from the active rear spoiler to the black band on the front apron. This high-tech meets pure sportiness.