The NY Times has a rather interesting Q&A with Steven Chu, the current Secretary of the US Dept. of Energy. There's a little bit more insight into him and his daily life. I especially like this part:
Is it true you don’t drive a car?
My wife does, but I no longer own a car. Let me just say that in most of my jobs, I mostly rode my bicycle.
My security detail didn’t want me to be riding my bicycle or even taking the Metro. I have a security detail that drives me.
How do you feel about adding carbon emissions to the air?
I don’t feel good about it.
I guess the president wants to keep you alive.
My wife is in favor of that as well.