That's the same thing I thought, until I got my Air (2012 model with the new charger).
Within my first half hour I had accidentally unplugged it 5 or 6 times, just by moving it around in my lap. Pick up the cord and plug it back in each time, it starts to get a little annoying.
I've gotten better with it now, but I will still do what this video shows, where it doesn't completely unplug. You don't always notice until you get a low battery warning when you thought it was plugged in the whole time :(
Has anyone else noticed you can move most of the design elements around and they interact with the balls. Everything except the Android holding the QR sign, the clock itself and the copyright line can be dragged around. The Google IO logo is the only one that you can move, but doesn't interact with the balls.