the only "dirtbikes" that are street legal are enduros. you'd have to have pretty much everything a street motorcycle has in the way of signal markers front and back, brake lights, special license endorsement, DOT approved tires, lighted license plate, horn, yada yada. then you'd have to convince them that there aren't any stability issues. good luck convincing conservatives of that, especially after the the wonderful reputation 3-wheelers left behind for ATV's. being that alot of ATV's are about as stable on pavement as nitroglycerine, there is a certain logic behind that. alot of the other hurdles i've read mentioned, emissions and whatnot could be walked around easily with mods in much the same way as street motorcycles and enduros. i'd expect insurance to run about the same as a crotch rocket. however, you have to remember that it's hard enough convincing state parks to allow ATV's (even though almost every one has horse trails and i've yet to see a horse trail that doesn't look torn up), much less allowing them to be licensed and driven as everyday vehicles.
bottom line, i'd be for it. hell i'd buy another large displacement quad just to put DOT approved tires and all the other things i'd need to be street legal. i just don't see if coming to fruition. i'd sign the petition without hesitation, but i wouldn't go hunting the DOT approved tires until it was passed into law.