Earlier quoted context omitted.
You're thinking too small. "it might link to a parking garage database of which parking slots are open" Imagine creating a QR code, (or copying one that already exists) which tells the car to fetch information from http://your.competitor.example.com/ . Then imagine going out late at night and sticking it on a busy motorway. DOS by traffic. Also. You better hope that your car doesn't have any vulnerabilities that can…
You're thinking way too tin hat. While we're there we better do something about all those people using radio jammers to down auto-landing aircraft. Also, you better hope their are no vulnerabilities in the automatically driven mono-rail / train system you are riding in. These type of issues are going to be discussed to the end of the earth but I can't wait to see driverless cars make their way from the lab to the car…
You're thinking way too tin hat.
I very, very rarely resort to ad hominem, least of all on HN, but your nickname says it all (if indeed VB refers to Visual Basic). Far too many computer problems of yore were created by VB programmers not being nearly "tin hat" enough. When engineering systems which can damage other systems or cause bodily harm, one's responsibility is to anticipate, mitigate, and prevent the worst case scenario to the maximum extent possible.