There was something I used a few years back that was pretty much what you describe. They eventually dropped support for their free accounts, so I stopped using the service. I'll see if I can dig up the name of that company for you...
Paul Graham argues the fear of looking bad is what motivates people. Based off of that concept I thought of the idea of a social network kind of like 43things with the major differences being:
- you can set a timeline of when you want to accomplish the goals
-people could rate the difficulty of the goals and you have a reputation based on how many goals you complete and the difficulty of them
- could be public or private
-could be more individualized, ie finish essay for English before Friday
I think it depends on the severity of the problem. If the problem is minor, an email should suffice. If the problem is of medium severity, a phone call or a conference call should be yield results. If the problem is very severe, it would seem best to gather everyone for a meeting in order to brainstorm.