I've been giving this some thought as I read through the book Getting Things Done. I've believe that for a list of activities to be truly productive, it does need to be individualized. If I were to try and have a single list that has more than one person I know contexts can resolve who is doing what, but there would be tasks that I would not want to put out for all to see (not that they are personal, but in my role they are confidential). Having two places to look for things starts to defeat the purpose of a single tool. My thought is then that the "project manager" (function, not necessarily role) would have a list of all activities taking place and flag them as "@waitingfor" if they are assigned out to other people. The other people would have to self-manage and make sure they have that activity. The PM would do regular follow up as usual for all @waitingfor activities.