Erik Möller, “Are Creative Commons-NC Licenses Harmful?” Podcasting News, October 4, 2005. Excerpt (via Peter Suber):
When the Creative Commons project published its first licenses in December 2002, it finally brought a sense of unity behind the free content movement….One particular licensing option, however, is a growing problem for the free content community. It is the allow non-commercial use only (-NC) option. The “non-commercial use only” variants of the Creative Commons licenses are non-free, and in some ways worse than traditional copyright law — because it can be harder to move away from them once people have made the choice. There may be circumstances where -NC is the only (and therefore best) available option, but that number of circumstances should decrease as the business models around free content evolve. The key problems with -NC licenses are as follows:  They make your work incompatible with a growing body of free content, even if you do want to allow derivative works or combinations.  They may rule out other basic uses which you want to allow.  They support current, near-infinite copyright terms.  They are unlikely to increase the potential profit from your work, and a share-alike license serves the goal to protect your work from exploitation equally well…..As we will see, there are many desirable commercial uses….[I]f you choose an -NC license, your work will not be compatible with Wikipedia, Wikinews, Wikibooks, and similar free content projects. One reason for this is that licenses like Wikipedia’s, the GNU Free Documentation License, work according to the copyleft (or…”share-alike”) principle: You can make derivative works, but they have to be licensed under the same terms. You cannot make a derivative work through addition of -NC content, as you can no longer apply the (more liberal) “share-alike” license to the entire work. Even where the license allows it, marking up regions of content as non-commercial and consistently following these boundaries is almost impossible in a collaborative environment….The use of an -NC license is very rarely justifiable on economic or ideological grounds….Finally, if you must use such a license for one reason or another, please do add an additional notice specifying the term of copyright protection you desire for your work. Otherwise, traditional copyright law will apply, and commercial use will be forbidden long beyond your death.