Unpaid overtime affects the labour market negatively

I am not one of those people that grumble if I have to work too much. Even with my current job, which is quite easy, I regularly come in before my shift officially starts to prepare my lessons, clean the classroom and get myself organized. I also tend to stay late to catch up on my students paperwork or reply to e-mails from the higher ups. But there is a point where this becomes detrimental, not just to your own personal life but, to society as a whole.
In good economic fashion, let's assume people who are paid a salary make more than those earning an hourly wage. So, perhaps, built into the salary is some allowance for unpaid overtime. Which I think is perfectly acceptable. You should try to go above and beyond expectations to prove yourself useful to the company that hires you. Further to that you can also think of putting in extra hours as a way to differentiate yourself from your peers as the better candidate for promotion.
However, working too hard for that future career is not always wise. If you put in an extra 20-30 hours a week (without pay) to move up in the company, the raises you receive barely cover the work you have already put in. It also means your boss has an expectation that now for an even better salary you will gladly put in even more hard work. It could be a bad precedence to set.
Paid overtime is a beautiful thing. I would happily put in 70+ hours a week if I received 150% pay for all of the extra hours; at least those in excess of what is a fair expectation of a salaried employee.
In Japan overtime is rarely paid. There is an expectation that you must do 'service time' before and after every shift. It also means coming in on the weekend when the need arises. Though there is no extra pay, it is a Japanese tradition to pay a bonus equal to 1-2 months pay twice a year so it may come out in the wash. During this recession, however, it is becoming clear that a lot of corporations are forcing people to work constantly. This is effectively driving down the hourly wage below the legal minimum.
Minimum wages disrupt the labour demand making unemployment higher than it would normally be. A lot of people argue that it is a reasonable limit to insure those who are able to find work are earning a living wage. But when the overuse of unpaid overtime occurs, there is no clear winner. Marginal productivity surely falls with the increased fatigue, unemployment still rises as fewer people are taking on the workload previously spread out and employees get burnt out; not to mention career satisfaction plummets. Although unpaid overtime is strictly illegal, corporations have been unhindered in the practice. Government enforcement during these times would help bolster employment numbers and keep Japan the world leader in productivity.