Teachers are accustomed to rewarding student performance with grades. Most mass collaboration software allows for the tracking of contributions, so it is easy enough for teachers to see who has done what, and issue a grade based on frequency. Similarly, teachers could also develop criteria for contributions (ideally this would be done jointly with the participating students) so that students would understand how the value of a contribution might be judged. On the one hand, my concern is that setting any kind of parameter on what constitutes a "good" contribution is going to undermine the collaborative spirit of the venture. If we set minimum and maximum contribution thresholds, I worry that students will feel coerced into making contributions, while others might be disincentivized to make as many contributions as they would have otherwise made.
Further, and more to the point, there is a prevailing notion of fairness that teachers try to honour in the classroom, that the inherent inequality of a power level distribution makes problematic. Effective mass collaboration appears to require a few self-selected individuals to do the majority of the work willingly, allowing the rest of the users to enjoy the benefits of this labour. The classroom environment is not typically set up to reward this kind of altruism, and views it's opposite, as a kind of freeloading parasitism to be discouraged, if not punished outright. Dealing with this view will require a fundamental rethink of classroom values.
