Amazon has taken a page from the Wikipedia playbook and launched SoundUnwound, a user generated music information site. They've gotten the ball rolling with info from their own retail site, IDMB and a few other sources and their own music staff will add to the efforts. But for the most part though the site is user generated. In typical Amazon fashion, however, they maintain far more control than Wikipedia. Most info will be filtered through editors (at least until you are a vetted poster) and no one can re-publish the info you're sharing for free.
My guess is that the end game is to integrate the info - if it proves worthy - onto the retail site; thus providing a richer consumer experience. Amazon already shares consumer reviews below each release on its main site.
