Creative Commons Posts βDefining Noncommercialβ Report
Last year I participated in a survey followed up by a focus group on the topic of Noncommercial Use, in particular around the context that about 2/3rds of the Creative Commons licenses extant use the NC attribute, such as in CC-BY-NC.
Defining "Noncommercial": A Study of how the Online Population Understands "Noncommercial" Use
http://wiki.creativecommons.org/Defining_Noncommercial
The topic is somewhat of a sticky one, as there are many competing interests. There are content creators who wish to profit from their work, there are other content creators who don't want anyone to profit (even themselves), and of course there are content creators who want everything to be free provided you share free content back.