The advice is "broken record" and it will be ignored by majority of young engineers. Working for a cool startup is very very cool. Working for big corporation is not cool (and considered evil if that corporation is Microsoft or Oracle).
And that is actually good for economy, for startups, for VCs, and for engineers (not in monetary sense but they will become wiser).
No, working for something like Google or Facebook in its start up days is cool. And that is like once in a 15 year opportunity.
In reality you can do a lot of things on the side in a 9-5 job. Than working crazy hours at a crappy start up .
Yes working at big companies is not very much profitable, but neither is working at a bad start up. Bad starts up are worse than big companies.
That is a far cry from the policy I experienced at MSFT. Doing free reviews on my own time of books being published by Microsoft Press on products I was an engineer on required approval from my VP.
Interesting. My first programming job was in a finance company who had a "we own everything you make, here or at home" policy. My manager said most finance companies would rather pay people more than have them working on things outside of work, which I took at face value. Knowing that was how I enjoy learning most, it was a big factor in my leaving.