Right now, there's no authentication when car computers communicate with each other…Time Magazine actually killed an online story posted on March 16, 2011 (see my post here) on an "MP3-trojan car-takeover"—possibly, I speculate, because it might give bad guys good ideas. Do a Google on "mp3 trojan car takeover" and satisfy yourself that once something goes on the net, it stays there.
My question, ever so humbly asked, is: Do you want to drive a car based on Microsoft operating technology? Think "Windows Embedded Automotive Operating System" and Stuxnet payback. Oooh, my lips go numb just reading that last sentence.