Why is it San Diego never makes these lists? Proximity to LA? Oakland's on there, and it's a lot closer to SF. Doesn't have a thriving tech scene like all of the others? Like Miami?
The startup scene is pretty much moribund for the 20-something:
The dynamic people left Qualcomm years ago--it currently resembles DEC or IBM of old.
Med/biotech is long term--if you're a 20-something who wants to get rich that isn't a great path. (Side note; biotech salaries seem to suck--it's part of the reasons why we have so many microbreweries--if you're going to be underpaid doing microbiology anyway, you might as well brew beer. LOL.)
Culturally San Diego is kind of a suburban wasteland--that means very little "Social Network Foo Yahooglezonsoft(tm) Buyout Bait". The "cool kids" are going to want to be in NYC, SF, or Austin with possibilities in LA or Chicago.
I don't know if anyone has studied the benefits of this but I have to say it's so nice to just be able to walk out the door of the office at lunch and wander around, sit on a bench, etc. Escape for 45 min - 1 hr and be refreshed. I think that's the appeal in more 'happening' city areas, even if we don't acknowledge or necessarily know it consciously.