When you start a project you have a firm vision of where it’s headed. You beaver away, working and over time you mould it to your vision. The vision may change, but it’s still your vision. At some point this, sadly, becomes a problem. With a group of people working on a project things will not always agree with "your vision". The direction of the project now needs to be moulded and controlled by the group, not by a single mind. It’s not always an easy transition, especially if the collective direction differs from your own.

While David Reid said this regarding Open Source projects, I think it applies equally well to entrepreneurship: when it's just founder, you do everything yourself, and thus everything is done exactly as you would do it. But when you grow your team, you need to hire people that you trust to handle their parts, and then let them do so. They're not going to do everything exactly as you would.