What do people actually mean when they define their content as “noncommercial”, and release it under a NC license? Creative Commons has released the results from A Survey of How the Online Population Defines “Noncommercial” Use. Their blog post announcing the release contains recommendations for when and when not to use a NC license.
One way to think about Creative Commons generally is of providing tools to prevent the failed sharing that results from relying on copyrights’ defaulting to “all rights reserved” — uses that you would allow but that will not occur because you haven’t authorized them (maybe haven’t even thought of them) and the costs of finding you and getting authorization are too high for the intended use (or maybe you’re dead and even scholarly use of your works is suppressed by your estate). This sounds dry, but think about the anti-network effects of failed sharing at the level of a society, and the costs are large indeed. Some have realized that too much use of NC licensing suppresses uses that a licensor who wants to share may wish to allow, at a cost to NC licensors and licensees and a greater cost to communities and the broader free culture movement — failed sharing, though at a much smaller scale than the failed sharing engendered by default copyright.