An issue that can lead to poor team performance is that of the rules or norms which govern the processes within groups. Each team will develop its own 'rules' about how they do things. Often these rules can be so team-specific that they exclude other groups. The sense of cohesion that this gives the group can be very useful. It can also be problematic in that some teams will develop one, two or even three sub-groups.
Remember that just because a group of people is called a team does not mean that they are one. Watch out for the real team within teams; these will be defined by norms of dress, sense of humour, language and a variety of other things.