You think the startup founders working 18 hour days are dicking around for most of that time? I'd say you're almost certainly wrong.
I'm not saying the post is wrong either, a good work/life balance might be the path to success. But the people who don't have that are not playing WoW all day at work.
http://news.ycombinator.com/item?id=209195
Barely anybody hit 10 hour days of solid productivity; typically, people can manage about 7ish hours of actual work, only 3-4 of which is coding or other heavily intellectually demanding tasks. This squares with several worker-productivity studies done around WW2 (when major corporations were deciding whether to move to the 8-hour workday; the standard at the turn of the century was 14 hours), which found that productivity decreases after 8 hours, and the time spent dealing with mistakes eats up any marginal increase in output. Having worked in one startup where much of the eng team seemed to work 12-14 hour days, I can anecdotally confirm that.
It's not that they're dicking around, it's more that they are probably staring at their computer screen cursing or berating themselves. Or feeling despondent and miserable about their chance of ever shipping product. Or writing code, but writing the wrong code which will just have to be ripped out once they think about the product again.
There's been a lot of research done into "ego depletion" - basically, 100+ studies have found evidence that the ability to focus and make yourself get things done is an exhaustible resource, and then recent studies by Carol Dweck have indicated that your abilities to do so, in some sense, depend upon your mindset going in and whether you embrace the task to begin with. The logical place to answer this would be with an fMRI study, and the first such study was just published a week and a half ago. The abstract indicates they found something, but the article itself is paywalled:
http://scan.oxfordjournals.org/content/early/2012/09/20/scan...
http://www.nytimes.com/2011/08/21/magazine/do-you-suffer-fro...
Say that we find that ego depletion comes from a shortage of blood glucose in the brain. If that's the case, the cure could be as simple as stocking the microkitchens with M&Ms (man, maybe Craig Silverstein had the right idea 14 years ago). It's also known that certain stimulants like caffeine and amphetamines help you overcome your normal mental fatigue limits - the problem is that they often tend to create dependency and lose their effect if you chronically overuse them. The reason for looking into the physical mechanism is that we might then be able to find simple solutions that work and don't have long-term side-effects.
There's a huge myth about Japan in that many people believe that salary men work insane hours out of dedication to their jobs. In reality, there is very little productivity in Japanese corporate offices. While the salaryman might stay for 12 to 13 hours a day, only 4 or 5 is spent actually working -- the other half is spent dicking around. They stay out of a social contract, a culture of not being the first to leave.
I think the kind of startups that we talk about here have a lot in common with the traditional Japanese corporate office culture.