Although I tend to think of overtime questions as non-constructive for the same reasons Mark does, my main objection to them is that they're simply not on topic.
The FAQ now has a pretty little diagram for everyone:
Here's the thing: Overtime isn't a unique subject for programmers. Lots of programmers tend to think it's unique for them, just as lots of programmers tend to think that about almost everything, but it isn't.
You want to see overtime? Check out the finance section of a publicly-traded company at year-end. I'm sure they can tell you a few things about overtime. So can sysadmins, lawyers, researchers, and many others.
Overtime talk isn't in the "All Programmers" circle, it's in the "All Careers" circle. It's a popular topic, yes, we all know that - any "pet peeve" thread is going to be wildly popular - but it's not something that uniquely affects programmers and definitely not something that programmers are uniquely qualified to answer.
Because there seems to be such a large audience who wants to talk about general employment and workplace environment issues, some folks went and created an Area 51 proposal for it. It's called Professional Matters. Please support it so that there will finally be a non-controversial home for them on the Stack Exchange network.
P.S. The other problem with overtime questions is that they are massively duplicated. Every question is practically a carbon copy of the last, with the essential question being some variation of "Should I put up with overtime?" / "How can I say no to overtime?" and the essential answer being some variation of "Familiarize yourself with the local labour laws" and "Your employer doesn't own you, it's OK to work 9 to 5." It's quite frankly stultifying to read those same threads over and over again. At some point we have to step back and say to ourselves, you know what, I don't think we really need another question about overtime.