I think this is borne out in the expectations of startups for their staff. The expectations for work is well over 40 hours per week. I think managements strive to get 50 or 60 hours per week out of their staff, and sometimes themselves.
Here's an example [attributed to] the CEO of Adbright, Ignacio "Iggy" Fanlo / firstname.lastname@example.org:
I hesitated sending this email for quite some time and had hoped that through your direct managers I would see some improvement. Having said that, I continue to see too few folks here at 9 AM; and too few folks here at 6 PM. I don't care if you are a morning person or a night person; if you want to work 10-8 pm or 8-6 pm, but I fully expect each one of you to put in 9-10 hours per working day. This is still a startup and we need more passion, time and energy from each of our employees than a large company would require. If we succeed, the rewards, both psychic and financial, will be great. But for that, we ask you to give more than the typical 9-5 job.
While I think this is completely counterproductive, and even if people are working 10 hours per day, I think this'll make them stop working those many hours, working for a tool like this, and find a job at a good company. Notch up one more Silicon Valley company that I will never work at.
But the sad thing is that this is fairly pervasive thinking, though most would have the good sense not to say it outloud, let along in a company-wide email.
It's great to have so many employers in the area, but I guess the lesson is that you have to choose an employer wisely.