We use Lost characters - Hugo, Ben, Kate, etc.

Homework and tests are two very different things - asking for help on a test = cheating. With homework though, you can look in the textbook, check wikipedia, etc. (where the answers are 'posted' as well, you could say) - that is the point of homework: to study the concepts and to prepare for an exam, which is the real test of your knowledge. I, and every student I know, don't hesitate - ever - to ask friends or instructors for help on homework if I need it. Facebook is just another medium for communication - I don't see why it should be any different from the spoken word.