There is a world of difference between a group and a team.
From a psychological standpoint, it can be said that a team has a collective consciousness, while a group only collective unconsciousness.
The easier, but less effective approach to team development is to encourage mutual understanding: workshops, team exercises, events through which team members can find out more about each other and not only in work related situations.
The more difficult, but also more effective approach to team development is through trial of fire: presenting a challenge great enough to break down individual barriers, reform personalities and bestow team identity to its members.
Of course, there is the question of risk. The biggest downside to encouraging mutual understanding is that it may annoy people and prove to be a time sink. The stress of team development by trial of fire may reduce individual team members (or the whole team) to ashes.