This might interest some of you:
http://wiki.creativecommons.org/Defining_Noncommercial
This is the long-awaited study on a large survey on how people
interpret the terms "non-commercial" and "commercial", like in the
NC-licenses from Creative Commons. Pretty interesting stuff for people
interested in free culture in general, although with its 255 pages
this might be something that you would rather like to skim through
instead of fully read :)
For a summary of the findings read:
http://creativecommons.org/weblog/entry/17127
-- Hay