For masses, bikes work great if the daily operating radius where you go about is something like five kilometers. But in Silicon Valley, except for some minor villages in between, 5 kilometers is only a couple of blocks. And instead of snaking through traffic in a city for five kilometers at slower speeds with your working clothes on, you would be sweating on your bike beside fast-going cars in a very much grueling environment of noise, heat, and an endless stretch of road. And then you would need to take a turn and do another five kilometers along another road.

I could see it working somewhat if you diverted all the bike traffic through the residential areas and punched the isolated culs-de-sac via bike paths so that bikes, not cars, could take a shortcut through the whole block instead of going along by the car routes. This kind of approach is very common in Finland: you can't always drive from one suburb to another but there's always a bike/pedestrian path that cuts through all that extra distance; here's a typical traffic sign denoting that: http://savepic.ru/7576556.png

But in general it's hard to see bikes becoming the popular vehicle for masses in Silicon Valley until there are enough towns the size of Copenhagen downtown and built with similar density, and where people commute locally.