In my OPINION, young drivers should not be allowed to insure a powerfull car until they have been driving long enough to have a full no-claims bonus, therefore will have several years driving experience, which hopefully proves they are a decent driver, having had no claimed accidents.. not full proof as not all accidents require a claim, but it would be a good start. A person with only 2-3 years driving experience is not enough to qualify them to drive something with 200bhp or more.
To those that say they think they are a good driver, only a fool thinks his driving is good enough to drive anything with high power, unless you have had expert training, which a normal driving test does not cover!
Edit: there was a show on lastnight that showed in USA, they have come up with a great idea which may soon be trialed in the UK, anyone with a previous Drink driving offence has their car fitted with a alcohol test unit, before they can start the engine, they must blow into the test unit, if they are ok, the engine will start, and at random time during the journey, they may be require to retest, and if they fail, the unit will tell the driver to pull over within a three minute limit before it turns the motor off.... great idea.