They used to call it "paying your dues". The fact is some of them will be exploited and get nothing, some of them will make a huge name for themselves and learn how to build businesses instead of following a traditional career path.

Personally if I had it to do over I would take my chances at being exploited in SV over the career prospects of doing things by the book in middle America; and fwiw I'm saying this as a college-educated late-comer to Silicon Valley (8 years ago at 28).