In any given project, any member may (_will_...?) leave the project some time into the future. If that project wants to base parts of its information sharing upon Diigo, then there should be a way of transferring an ownership, and actually provide co-ownership of any group.
It could also happen that a member dies or is left incapable of even doing such a transfer after an incident. So a co-ownership feature would solve such things proactively.
It could also happen that a member dies or is left incapable of even doing such a transfer after an incident. So a co-ownership feature would solve such things proactively.