Having multiple project managers that work on different parts of project management would not be a bad idea under two conditions: 1. The project is a huge undertaking where there is too much for one manager to manage and 2. They have their own manager or supervisor to report to. I believe the second condition is necessary because without it, their is a bigger chance of there being a power conflict as the managers step on each others toes trying to do what they think is best to overcome any obstacles and would just cause more obstacles in the long run. With a supervisor of their own whose only responsibility is watching over them and making sure they work together rather than against each other, the project is more likely to be successful with multiple project managers working with their teams. The first condition is pretty self explanatory, there is no reason to have multiple managers on a project where one manager can handle the responsibilities alone just fine.