The MusicBrainz data has been used in a very interesting MIT paper that discusses illegal music downloading, Napster and the sharp rise of people attending music concerts. ARS Technica writes:
For album sales, the researchers accessed Nielsen SoundScan, the music sales data service, and looked at aggregate receipts from 1993 through 2002. The paper also examined data provided by MusicBrainz, a site that allows users to create relational databases about their favorite artists or music genres.
Since file sharing technologies made millions of songs freely downloadable over the internet, they were naturally expected to displace legal sales. Most empirical studies have found evidence of this displacement. However, while file-sharing decreased legal sales, it almost certainly increased the overall consumption of recorded music.
It is nice to have some of these things I suspected confirmed — especially with the use of our data. :)