But, as noted, this type of discussion probably belongs elsewhere...

Actually, no. It seems like it would be the problem of the poor sod who went to the trouble of writing an exam.

If $A$ and $B$ are bounded non empty subsets of the reals, is glb$(A)\le$ glb(B)$? Upon prompting, the OP agreed that the question should have also said that $A$ is a subset of $B$.

A MO member (OK, a student) suggested posting in on SE.

If someone asks me a question, I will do my best to answer. And this on MO, math.SE, the bar at my university, #math, &c. If they should not have been asking it, it is their problem.

I can't claim any "unfortunate sense of propriety" as I was really following the example set by Matt Daws, cf. this question. To be fair, I had intended to move the question over here in the next few days if no solution turned up on MSE. But thanks for the moral flattery :)

I can assure you that as soon as the moderators see these things they get deleted, and if they don't see them fast enough the 20k users (which are capable deleting closed posts immediately without a day+ waiting period) usually do that.

You are wrong to say, by the way, that math.SE is not "run by people in the mathematical community". It is true that the software and the servers are maintained by the SE guys, but the moderators of the site are two "fully licensed" mathematicians and two mathematics students (there should be another moderators election soon). All of which are also MO users by the way. No one supports cheating on math.SE, the fact that people are willing to help with a homework problem is a whole other thing. When a user is found to be using math.SE for cheating in take-home exams (which is a whole other thing compared to asking a homework question) they are almost always banned (I cannot recall a time when they weren't).

Dishonest people existed long before the internet and math.SE (or MO for that matter), and they will continue to exist long long after the internet will collapse and we will resort to carrier pigeons sending binary strings across vast distances again. Had the said student used a different forum? IRC chats? Usenet? went to a different university and asked a professor there? How would that be any different?

If anything the fact that the student used math.SE made it visible and easier to know that someone has been cheating.

I understand that this is how the system in the USA works, but you have to remember that a lot of the users on the internet are not from the USA, and are not signed on this strange "honors code" which disallow discussions like that. If people respect the honors code, then surely most of the student asking homework questions are not those signed on this paper to begin with.

Lastly, I should point out, people that cheat and fail tackling problems are not likely to become competent mathematicians, and will likely fail or retire from mathematics eventually. People that enjoy mathematics, even if they do get the solutions given to them, will sit to understand them on their own. How different is that from finding the solution in a book or a journal?

(Yes, I am well aware - from my own experience as well - to the vast difference between reading through an endless pile of books and asking someone, even your professor, for help. However if you wish to learn you will learn. The powers of curiosity are amazing.)

Writing a complete and detailed solution to one problem with explanation on how the method works can have much better results. I agree that students need to learn how to tackle problems on their own, however you must have some basic tools in order to tackle problems. Sadly, not all teachers are that great and some students really fail to learn from their teachers. In that aspect I find that helping other students - even in their homework - can be very useful for their development.

How do you drop an empty set?