Bad example. The folks I know at Apple are ridiculously overworked. I've got a cousin who works on FileMaker that's been putting in 12+ hour days and weekends for the last year. I've got a friend who works on iMessage for the iPhone, and his roommates never see him at home unless they specifically arrange a social event with him.
I think that if you want a company in Silicon Valley with decent work/life balance, it'd probably be Microsoft, Adobe, Cisco, or one of the other last-generation giants. Google depends on your team; there're parts of Infrastructure, Apps, etc. that work reasonable hours with little deadline pressure, but people on the money teams (Search, Ads, Android, Doodles) are often there at all hours because they set very ambitious and complex goals for themselves. Facebook has a reputation for long hours and weekend hackathons. Yahoo is apparently very variable: some folks are putting in 12-14 hour days and still not getting all their work done, while others work for like 2-3 hours and spend the rest of the day on Facebook. Apple I already mentioned.