You kill the magic of a successful team if you spread them out. If a team works great together, you should keep them together. The team dynamics are a lot of that success.
Sometimes, it really does help though. The team running Windows 7 and now Windows 8 was the core of Office (Steven Sinofsky, Julie Larson-Green, Jon DeVaan). They really helped shake off the engineering problems during the Vista timeframe and enabled a really cool, successful product in Windows 7. Same with Terry Myerson (mentioned in this article) and his success first with Exchange and now Windows Phone.
I am not familiar with what happened there, but the way you describe it, that is not "spreading around" a team, but moving an entire team to a new project.
Spreading around a team is like spreading around a kindling fire. Moving it to a new project is like adding fuel.
I don't disagree with this. But I read your comment as moving people to another team couldn't make that new team any better. Perhaps I just misunderstood.