Teams that are too close have their innovation diminished.

We have a tendency to want to work with friends, but it turns out that this inhibits creativity. We need new people in the team as well.

It is unlikely that a team that has worked together for a long time will come up with something really original. 

So add some diversity. If you want your team to be agile and innovative then do not recruit new players who will ‘fit in’; choose people who will challenge the group’s thinking.