Is it unethical to ask for homework help on StackExchange? Sometimes when I have been struggling on a problem set for a while, I'll post a question on StackExchange, openly acknowledge that it's homework, and ask for hints (not the full solution).  Typically people give good advice and help me think about the problem in several different ways, and I end up learning a lot by asking the question.

Now the thing is, we are probably not supposed to ask the Internet for homework help.  But in my classes it is perfectly acceptable to go to TA office hours, where most of them will tell me the entire answer instead of giving hints.  Often I've seen TAs present the solution on the blackboard in front of about 20 students (because all the students need help on the same question).  We're also encouraged to "collaborate" with other students, who will usually tell you the entire answer instead of giving minimal hints to help you along.

Is it unethical to ask for homework help on StackExchange given that I learn a lot more than I would using officially sanctioned methods?

(If it matters, I post on math.stackexchange, and this is for classes like real analysis and abstract algebra.)
This might depend on your university's policy on cheating and plagiarism.

For our university (though the precise details may vary from course to course), you are allowed to use StackExchange to help you to understand concepts, but you are not supposed to use it to help you solve assignment questions. 

We tell the students that if there is any risk that they may have read an answer or some code or whatever that might have influenced their answer, then they need to cite it. With a proper citation, they cannot be accused of plagiarism. We may, however, ask the student to answer extra questions in such a case, in order to demonstrate their knowledge.