This a good question. Team are good for several reasons. First, teams are manageable in size. Therefore, teams can get a lot of work done in an efficient manner. It is important to realize that too many cooks can destory a kitchen. Second, teams can also focus on a specific task at hand, especially if the team is filled with people that have specific skill sets.
There are also downsides when it comes to teams. First, if the teams are not coordinated, then it will be hard to use the labor and fruit of the various teams in a way that flows and coheres. In other words, the multiplicity of teams can create a dysfunctional organization. Second, with little communication, teams can do redundant work or even not do important work.
In short, teams are effective, as long as there is good communication.