Can you expand on this point? Is there something that you can point to that is structurally different in SV that cannot be replicated elsewhere eg. infrastructure, legal environment etc...?
For example there is nothing very early stage in New York that wields the respect and track record of YCombinator or SV Angel. Both of those have become institutions in SV and are very important as connectors and seed stage investors.
The Stanford ecosystem is another example that is well oiled. The Cornell Tech campus in NYC has tons of potential, but it's still quite new.