Is Silicon Valley's run going to end shortly? Will they get #piped?

Could Silicon Valley 2020 be heading the way of early-1980s Detroit? It doesn't seem likely, but signs are there. Nothing lasts forever.

People have been claiming this for years -- hell, I did a podcast about it recently too -- but this new article on Harvard Business Review lists four main factors for the potential demise of Silicon Valley:

• The biggest companies there have become overbearingly big.

• There hasn't been a good IPO in a minute, and there have been some real fumbles, like Uber …