an executive summary of the 2009 Formula 1 rule changes narrated by Sebastian Vettel
The target is to improve overtaking, making for better racing action and fan enjoyment, is realized by moving back to slick tires, and marginalizing the wings and aero appendages to enact a reduction in downforce accompanied by the introduction of KERS (Kinetic Energy Recovery Systems) http://formula-one.speedtv.com/article/special-f1-2009-a-step-into-the-unknown/
The most important job of the Overtaking Working Group (OWG) is to improve overtaking in Formula 1 and the OWG has been formed by three of the most respectable technical engineers in the sport – McLaren's Paddy Lowe, Renault's Pat Symonds and Ferrari's Rory Byrne
The main reason why rear diffuser designs have been modified recently, as well as front and rear wing formats was to make sure cars that want to engage themselves into an overtaking will not suffer as much from the pursued car's air flow as before.
Mishi and Peter of http://stipistop.com/ finds the coolest stuff!