Stuxnet spread via usb stick. That's an inconvenient way of infecting something specific. My crystal ball is hazier than Schneier's, but having more potential vectors makes doing something like Stuxnet easier.
Again, I disagree. There's this leap of faith that the more things are connected to the Internet, the more damage can be done... but the things that can do damage could have been connected to the internet a long time ago and they don't. It's stupid that Chrysler's control system allowed disabling the vacuum assist on the brakes. But it didn't disable the brakes. Theoretically, a hacker could kill the regenerative braking on your Prius. But they couldn't kill the brakes on your Prius. And it's great that Schnier is raising the hue and cry about this stuff because the first big dumb things that are going to be automated are semis and hell to the yes you can cause a shitton of damage with a rogue semi. But the hue and cry should be "we should worry about this stuff" instead of "ZOMG we need to worry about EVERYTHING" which is what these articles tend to be.