Random Observation: CalTrain #324, an express train southbound from San Francisco to San Jose, was quite full when I boarded, at the Hillsdale station this morning (2013-06-19). In Palo Alto, I think more than half the train cleared out. In Mountain View, almost everyone else left. There are now two people, besides me, in the visible seating (about 5/12ths) of the car I'm in, whose only other stop is San Jose.
From this, it seems to me, one of two things can be inferred - though it's possible it's a mix of these, and likely that I'm missing some possibilities:
(1) Living in San Francisco is desirable enough to commute down to high-paying silicon valley jobs, and/or:
(2) a bunch of people who work in Palo Alto can't afford to live in Palo Alto.
Just randomly thought that was an interesting thought. I wonder what the reality is, behind why people were on that train.