Experience in the industry validates quite a bit of what was said here: communication definitely is key in leading a project and in working with team members. What I have seen is this: team members would often be proactive in telling the manager (and other team members for that manner) when they would not be available or if they would not be able carry something out due to bandwidth constraints. This would happen because the manager established the precedent that the team should take ownership of the project and let others and manager know if something is coming up that would need to be addressed. Once the communication would be done, the team would work out a plan to cover for the abscence or find a way to help the person do what they needed to do to carry out their tasks. It is very much a give and take relationship between manager-team and even between team members. The key is definitely PROACTIVE communication. (communication would be rather useless if it came late).