This agrees with what I see, but megacorps and in general many large organizations are often slow to move both in and out. They can take years to stop building

This agrees with what I see, but megacorps and in general many large organizations are often slow to move both in and out. They can take years to stop building up experience in areas that changed from being a new promising technology to mature fields to oversold fads. They also have a lot of money help weather many overpriced hires. So I am not sure that megacorps hiring is a very strong counter-argument. Just my 2c. However, megacorps do not seem to suffer much for such continuous lagging in hiring. I do not know why this is so: is it that they still hire smart engineers who can easily change groups and fields or do they work on their core technology to help build the next peak (after the debris are washed away in a fad crash there is often a technology renaissance).