Wired has a great interview with John Maeda. I especially love this quote (emphasis mine):
With regard to what is designed really well, I think people are the best-designed objects in the world. Seriously. People can handle all kinds of shit all day long, and they're still alive at the end of the day. They're so robust. They can adapt to any situation. And they also know when to stop. They'll say, "Hey, I've had enough." And they'll go out for a smoke or a drink.
I'm afraid people don't always know when to stop, though. But a little is better than nothing.