How do you draw the line between legitimate homework help and cheating (See Details)?

Homework questions (or what appear to be such) are commonplace on Fluther and other Internet social Q&A sites. Some users avoid answering any and all such questions, feeling that asking for outside help is always cheating. Others will answer even the most obvious ones, like complex math problems not related to the real world, but just asking to solve a certain equation given a specified set of values. Some see a line of distinction somewhere in between.

Take a creative writing class, for instance. Even excellent professional writers might reasonably use the Internet and a Social Q&A site to solicit opinions on a topic they must cover, gather alternative points of view, or to see if someone can provide them just the right word or short phrase to capture a larger concept. On the other hand, when a calculus student posts an equation and asks for someone to provide a solution and show the work, I think mist of us would agree that the student is cheating, and if successful, will go through all their homework assignments without ever learning how to solve differential equations. Perhaps they will copy the work of a nearby bright student, and even graduate with a good grade, But the dolt will never know how to solve the equation, and won’t be able to hold down any job where such a skill is needed.

So where do you draw the line? What’s legitimate Internet research, and what’s asking someone to help you cheat by doing your homework for you?

This question was inspired by one from @anonini asking for a good word for a concept, ’‘Is there a word or phrase that sums up this quote?’’. In particular, note the debate between @Jeruba & @papayalily regarding this issue.