Warner Music has bent beneath the force of the anti-DRM winds sweeping the globe. The label will now offer its complete catalog, DRM-free, through Amazon's new MP3 store.

The announcement means that EMI, Universal, and Warner now offer their catalogs in DRM-free digital formats, making Sony BMG (of rootkit fame) the lone holdout among the majors. Amazon now claims to offer for than 2.9 million songs in MP3 format from over 33,000 unique labels.

Warner's announcement says nothing about offering its content through other services such as iTunes, and represents the music industry's attempt to make life a bit more difficult for Apple after all the years in which the company held the keys to music's digital kingdom; no one could sell major label tracks to iPod owners except for iTunes, and iTunes even become a go-to destination for non-iPod owners who wanted a simple, cheap way to pick up some songs. Now, with the move to MP3, the labels that have chosen to open their music have a way to encourage multiple download services to flourish, keeping labels safe from being dominated by any single digital distributor.

The move comes just before Amazon plans to give away one billion tracks, a promotion that will begin with the Super Bowl in January, and Warner was no doubt interested in jumping on board the promo train before it left the station.

Will Sony BMG, which has apparently never met a form of copy protection that it doesn't like, follow suit? The "Mene, mene..." is already on the wall, and it looks likely that Sony BMG will go DRM-free, too, by the end of 2008. The entire movement to free music from DRM's shackles has had stunning success in 2007 after years in which such widespread moves to MP3 looked impossible. Could movies be next?