Yeah, it's been talked about before..

http://empeg.comms.net/php/showflat.php?Cat=&Board=wishlist&Number=24132

http://empeg.comms.net/php/showflat.php?Cat=&Board=wishlist&Number=60237

And Peter at one point (back in the day when empegcar development was more active) said some kind of rating system would make it into a future release. I suspect this kind of feature is something that has fallen into the category of "we'd like to do it, if we had the time" though.