I've seen many organisations where project managers would reason like this:
We specialise in very small projects. Since a very small project needs a very small team, I should allocate one person or two to each project. However, this means that only a couple of people in the organisation know about the project; if they leave or are struck by a bus, the project is doomed. Therefore I will allocate four or five people to the project just in case, despite the unnecessary overload.
I can understand that a project manager may be concerned about an employee quitting and leaving the project unmanned; that would be disastrous. However, compensating by making four or five people work on a very small project that only needs one or two doesn't look like a good idea.
What other strategies can you think of to minimise the risk while preserving resources?