This is a very uncharitable view. Those types would exist at any company. There is pretty high turn-over at the large companies as well. People can be there to

This is a very uncharitable view. Those types would exist at any company. There is pretty high turn-over at the large companies as well. People can be there to help build their resume, help make connections, learn the ropes at a large company and gain technology exposure, etc.. My time at Amazon, I did see some people leave to form companies. Generally it was when someone particularly smart found a clique of a few other smart people and they then all quit and go off and do something else.