we have staff that comes and goes. whoever is on our current staff can collaboratively create and edit and share tasks and task lists. but if we use Remember the Milk, if someone leaves the organization we have no way to unshare a list and thereby remove their access? No way to reassign their tasks to someone else?

If this is really the case then I am sad to say we cannot user RTM. And I just spent all morning playing with it and was all excited about integrating it with our Google Apps calendars....

:-(