When people know one another well, they are much more likely to work well together. Watch teams who have a new member; typically, that new member will remain somewhat isolated until everyone else gets to know her. If you have several employees who are barely on speaking terms and you throw them together into a project, it will take some time for them to break the ice and begin to work well together. Conversely, team members who already know, like and respect each other may be more willing to collaborate for the betterment of the project.