I personally have always enjoyed working in teams, however like individuals, no team is without fault or limitations. However, I think it is safe to say no huge undertaking can be completed alone- regardless how talented the person attempting the project is. I also think even small undertakings that could be completed alone are often improved with the help and insight of others. I think working in teams allows for specialization and for more to be done in a shorter amount of time.
However, working in teams can sometimes make things more difficult. Working in teams requires establishing a central goal, communication, and for every action to be approved by everyone on the team. I think that for this reason not every task requires the use of a team, only ones where there is a large enough workload where everyone can contribute and where multiple viewpoints will be helpful. In class we also mentioned the element of a deadline. Deadlines often imply that a final product is involved and I think that is necessary for a productive team. A team needs a common goal and without a deadline there is often not a concrete goal to speak of.
In short, I think teams are great options for many different types of projects, however it takes some effort and a common goal for a team to be successful. When all members of a team are willing to work together the best work is produced.
I agree with you that a team needs a common goal, but in practice is often missing due to work overload and time management. Understanding the goal makes things much easier and the final result more productive.