If a course is shared by many teachers and where each teachers' students are in different groups in the course, there may be instances in which one teacher decides to add an extra assignment. It would be great if the teacher could make the assignment and then check which groups it should apply to. The other groups would not see the assignment (and it wouldn't show up in their gradebook).
Potentially this feature could be added to any aspect of Moodle to enhance teacher collaboration without requiring Metacourses.
This discussion http://moodle.org/mod/forum/discuss.php?d=138484 has the details.