The three problems that come with scale from Michael Lopp (aka Rands):
Second, a rule: the addition of each new person on your team increases the cost of each of the following:
1. Communication. How much effort is required to get Idea A and make sure it travels to all the necessary people?
2. Decisions. How quickly can a group of people best choose Path A or Path B?
3. Error Correction. How long does it take to detect and fix when something is going wrong?
How does your organization solve these problems? Read his post on project managers for answers.