How much homework?

What is the ruling on homework?  What is too much? What is too little?  As a teacher and a parent I can definitely see both sides of the fence.  As a teacher I truly only assign homework when it is necessary and are not going to give lame assignments just to be keeping the students busy at home.  But I am social studies teacher...if I were a math teacher that might be a little different.  From the parent perspective I like that my children have homework but there is a time when enough is enough.  Some of the assignments that my children are expected to complete are quite time consuming for a one night homework assignment.  So as a teacher and a parent I think that homework should only be assigned if it will help to benfit the student and not just keeping them busy after school.