[thaumasiotes]

You can get people to do work based on the strength of a personal relationship, sure. I once gave an unexpectedly long assignment to a class of about 30 students, and ended up getting six completed assignments. One was from a student who was just absolutely determined to be "a good student". The other five were clearly done on the basis of my relationship with those five students rather than because they thought it was a reasonable use of their time.

I don't think that approach can scale, though. You can't maintain that kind of relationship with 50 people; you need them to enforce the norm ("do the work!") on each other.