[yongjik]

Well, I'm sure having a linear string of cities helps, but effective density is higher everywhere: Switzerland is the norm instead of the outlier.

E.g., San Mateo and Santa Clara counties, at the center of Silicon Valley, have population density of 663 and 580 per km^2. And of course San Francisco has a whopping 7249 per km^2. They also have a string of connected cities, thanks to being constrained by the pacific and the SF bay from either side.

I don't think I have to repeat on HN what the infrastructure looks like in the Silicon Valley.

* Besides, your argument can be paraphrased as "Of course it's easier in Switzerland, because it's filled with mountains!" Think about it.