I think the warning signs of a 'gold rush' are when ethics go out the window (most recent example is the mortgage industry). Capitalism is all about going where the money is but if the correct rules aren't in place and the culture isn't strong enough the whole system goes to hell like a badly moderated news forum. The key question about SV of today is: are the correct rules and culture in place to keep the gold rush healthy and sustainable?
And Silicon Valley has been "about the money" for 20-30 years now. When Wozniak left Apple is a good milestone for when it became "about the money".