Trust is the sister of responsibility.
The reasons for implementing a system with a large team are varied. The most common one is that the scope of the project is too large for a small team to handle. However, some large projects would be better off if implemented by a small team. Even if the scope is large, a small team may be faster or more effective, mainly because communication is not as likely to prove a problem as it is in a large team.
Sometimes, the use of a large team is politically motivated. The size of a team may signify the importance of the project and of the project management itself. Author and consultant Tom DeMarco discussed this problem during OOPSLA 2001.1 He indicated that surprisingly ...