I thought the reason you really shouldnt use a moto helmet is that they are not fireproof, when i raced karts i had a arai gp helmet, cost me like $650, and that wasnt fireproof, not that a kart could really catch on fire, but now that im building a car for the track, ive bought a snell approved bell sport helmet, just personal preference i suppose. I mean you have to wear them for a long time and the buckles on moto helmets dig into your neck and are generally pretty poor quality compared to a high end helmet. Personally i wouldnt wear anything else, but thats just me