What are the ethics of homework help on this site?

Many questions on this site pertain to homework, ignments and the like. What are the responsibilities of the people who answer the questions? I always try to "walk" the questioner to the answer but always leaving the last mile out. However, I notice that other people just barge right in and give the complete answer along with how to get there (presumably in the hopes of getting more "best answers"). Is that ethical for the answerer? Is it beneficial to the questioner?