Pretty much my experience of group work: good students who want a good mark have to carry the unmotivated because they do not want to take the hit on their grades, while there are essentially no consequences for one or two students doing nothing.
There is a lot of lip service given to using group work to teach collaborative skills, but the cartoon reflects what students actually learn; i.e., that group work is a fraud. As I have stated before in this blog, group work can only contribute to learning if relevant theory on group dynamics and instruction in practical collaborative skills have been explicitly taught and assessed, either in the current course or a prerequisite. Even then, successful group work requires considerable preparation by the instructor to carefully structure tasks, distribute the workload equitably, and have clear and thoughtful assessment. I have seen this used appropriately in a few rare programs, but the true purpose of the vast majority of group work assigned is merely to reduce the instructor's marking load. Bah humbug!
Given motivated students and topics students care about, small group (in-class, ungraded) discussion can work well, provided students are given structured activities (e.g., a series of questions to discuss) and a clear time limit (to stay focused).
Any other group work that requires students to get together outside of class discriminates against students with long commutes, single moms, students working their way through college, mature students with elder care issues, minority students whose family or cultural expectations prohibit their participation outside of school hours, or etc.
Group work for marks where the group processes are not directly observed and assessed by the instructor make it almost impossible to assign grades fairly.
Where groups are allowed to chose themselves, 'A' students will strive to join together, excluding not just 'B' and 'C' students, but also anyone with a visible disability, member of a lower social class, any member of a cultural minority, and so on. Group work where group members are not assigned by the instructor are therefore inevitably sexist, racist, classist, abilist, and so on. Instructors who do not assign students to groups must recognize that the primary purpose of group work in their class is to ensure the reproduction of the current social order rather than to certify achievement based on talent and effort.
Assigning students to work together in groups ensures that A students will be frustrated by having to do a greater share of the work to ensure a minimally acceptable grade and/or accept a significant 'hit' to their grade point average. Assigning students to work groups without adequate training in group collaboration skills and appropriate checks and balances on workload distribution and task assignment ensures group conflict, and an end product that is greater mess than the sum of the flaws introduced by each individual.
I'm not a fan.