That's a good point. The health-risks of overwork seem to match well those of having too much 'fun'.

My guess is that the hidden psychological motivation is the same: to avoid addressing personal problems.

Exercise can help but even there, it depends. If you keep moving your body around forcefully for extended periods you risk heart disease and stroke, e.g. dancing plague of 1518.

Or how about work in general? If doing something 6 hours a week is borderline what is doing something 40-60 hours a week? Assuming most people work for money, isn't this just an extreme cultural addition to money?

My work, as in day job, usually consists of 3-4 hours working with 3-4 hours having lunch, chatting with colleagues, staring at the window, reading reddit/HN/LJ, doing some 'transparent' research on my startup. And that's when I'm working hard.

Working on my startup could easily drag me into a 8-10 hours race with only a few tea breaks.

If by addiction to money, you mean necessity for it to pay the bills, then this is true for most workers.

I suspect those of us electing to work upwards of 60 hrs/week at startups have other issues to work out beyond the allure of money.

I don't think it's fair to say it's an addiction to money. That may apply to some professions but a lot of people working 40 hours a week are just making enough money to get by.