An interesting law review Note examines the tendency for high quality uncompensated fan dubbing of anime (i.e. Japanese animation films) to lead to the commercial failure of poorly dubbed anime which are licensed. The Note asks if there is a room for considering the unlicensed fan dubbing to be fair use.
The issue is a variant on a related issue, which is copyright liability for translations when the owner of the original work refuses to make a timely translation of the work into the translator's language. Some countries provide express exemptions from liability or mandatory license regimes to address this issue. Essentially, what fandubbers are doing in the cases discussed by the Note, is the same thing, to the extent that the commercial translation is too shoddy to capture the original work.
The article is also a good example of the power of the Internet (which is a typical means of distributing fan dubbed work) to coordinate and harness uncompensated work for which the Linux operating system, wikipedia, the blogopshere, and web fiction (partiuclar webcomics, often in the Japanese manga tradition) are other important examples.