Autoblog

If I remember correctly, those fans are too keep the person sitting in the seat warm while the top is down. This was first seen in the new SLK.

A pair of fans "embedded" in back of headrests - extra thrust? Come on, who wrote that nonsense? Check out the SLK model, and you`ll see that these fans are actually something Mercedes likes to call airscarfs:
"Airscarf uses ventilation outlets in the seat to circulate warm air around your neck and head. You control the temperature from the central console, and the airflow adjusts to the vehicle’s speed."

more advanced(possibly) version of the airscarf system providing heating to the neck during cold weather motoring. It could also provide cool on really hot days??