From what I've seen out of the current Task implementation, is that each Task currently only has 1 owner. If we wanted to make a Shared Task that multiple people were required to complete and/or work on...there seems to be a gap to handle this use-case. Currently, the only way I see to do a "Shared" task in the current Clearspace 2.5.x and believe this is the same for SBS 3.0 are to:
Perhaps there is room for here for a new feature in Projects:
Given that there is such a big gap from a single person to a full-blown project scope...something that allows Tasks to be defined to a sub-set of users...would be highly efficient and useful on a global scale.
+1 for this concept - I just had a user ask for it.
Also thought this could be handled via Parent-Child task relationships. A parent task would not be considered "complete" until ALL child tasks were checked off. But perhaps that is subtly different from what you've outlined here...