I was just in SF and about to go there again today. Everywhere you look in the financial district, there are new towers being built. There has to be 20-30 new tall buildings being built. They aren't empire state buildings, but there is no doubt a big boom in construction.
I think in a free market, tall buildings can be a sign of wealth in an area, although its not the only indicator. But I'm concerned because houses in the silicon valley or doubling in price, and there are endless construction projects.
All up and down CalTrains, the train that goes up and down the silicon valley, there are massive and I mean massive condo communities and giant apartment complexes being built. The crazy part is that they are getting high rents (2,000+) and are 95% filled up. There is more construction being built now than I remember before the last housing boom. I don't know if this is because of the Fed or because of other factors (a lot of the tech companies got huge tax breaks), but construction is booming at a scary rate.