Having grown up in Silicon Valley, I can honestly say that what people consider to be Silicon Valley today was not anything close to what it was 20 years ago. So I don't take it so seriously anymore.
Since San Jose went from the gateway to Silicon Valley to the Heart of Silicon Valley, I feel like San Francisco, which is actually part of the Peninsula, can be part of SV.
I've only been here six years, and truth be told I avoid SF at all costs, but all I have to do is look at the job listings. SF listings are full of every Social Web Media Infinity-point-Fad known to man.
South Bay -- Platforms, infrastructure, embedded systems, established technologies, emphasis on availability and reliability. This is what the San Francisco startups rely on to make sure their new web startup doesn't fall over at the first sign of traffic.
One might see this as the traditional Silicon Valley maturing and even stagnating in comparison to San Francisco's young, hip, fast-moving culture, but I don't think it's reasonable to treat them as a unified entity.
I agree there is this trend (the hip Social Media whatever startups are loss prominent in SF), but you do see some lower-level silicon valley startups in SF. Salesforce, Riverbed Technology, BitTorrent, Heroku, Dropbox, Square - just to name a few known ones. Admittedly there is few electronics stuff here (outside of biotech).
That said the Bay Area definitely has an OSI model going, with the lowest levels in the SE extreme (santa clara, san jose), higher levels NW (Mt View, Palo Alto), and software applications all the way to SF.
@thomas: Salesforce is actually bigger than Facebook by heads and HQ'd in a few skyscrapers in SF.
(soon to move to a dedicated office complex in Mission Bay.)
Well I think it has to do with how difficult it is to find affordable office real estate for businesses that outgrow their space. I can't imagine a company as big as Google or Facebook having their HQ in SF without having to build a giant skyscraper in the Financial District.
I think its important to keep in mind this is very tech specific and generalization and doesn't refer to the life style or atmosphere of either being the same.
Many of the engineers/designers tend move around all over the bay area. Also, the investors are the same for a great portion of these companies as well.
It's just easier to refer to it as "The Valley", although it's technically not correct.
It's just one of those things where people not close to the subject get a distorted opinion, sort of like Chinese whispers. Like the (probably totally exaggerated) idea of some Americans thinking that people from the UK are from London. Like when tourists stop you in the streets of Oxford or Cambridge (presumably other places too, I just haven't lived in them..) and ask "excuse me, can you tell me where the University is?".
When I was first aware of Silicon Valley I literally pictured a road running through mountains, with big company X on one side, Y on the other, next door was Z... then after that I just thought of Silicon Valley as the techy nickname for SF. Then when I cared more, I grew to know more about it.
Having grown up in the midwest, now living in SF, and commuting daily to SV, yeah, most of the world thinks it's the same thing. SF is just a suburb of SV.
