+1 on needing this feature. I upgraded to Pro and spent hours transferring all my tasks from Remember the Milk to Toodledo, only to find that the sharing does not work the way I need it to. This feature worked seamlessly in Remember the Milk. I am sad to say I'm about to switch back to RTM because of this missing feature in Toodledo, which is otherwise the far superior application.
PS - Are you planning to offer an option for users to integrate their workspace with the workspaces of others who are sharing with them (i.e. show folders they own AND folders others own and have shared in one view)? Would be nice.