Most students (and many faculty) do not like group work. I have maintained for a while that one of the reasons is that faculty assume that by putting students into groups, they learn how to do group work. To think that students learn how to be a contributing group member when we never teach them how to may be a bit naive.
Here is a link to a good discussion on structuring group work and helping students actually learn how to work in groups. http://www.facultyfocus.com/articles/teaching-professor-blog/five-things-students-can-learn-through-group-work/