[mr_tristan]

There are a lot of people living further away from the city commuting in than people that live near BART or caltrain stations.

Anecdotally, half the office (in a small startup) I worked with drove to a BART station, then took BART the rest of the way.

Also, I'd say the sprawl goes pretty far. I grew up in Vacaville, and it was not uncommon to commute into San Francisco. That was 50-something miles away.