I should first remark that this news isn't really about a co-op feature or anything. But then again, it is about getting somethings nice for free. So, I don't think you'll mind.
Some say that promotion is everything. Companies spend billions of dollars to promote their products. There are TV ads, billboards, and so forth. However, being the frugal person that I am, I believe that there is a much better way to promote your product: give us something for free.
Thankfully the team at Blizzard are listening, because via iTunes, they are offering a 100% free Diablo III song. Kotaku has the details on how to download the file, but all you need to know is that the song is called "Diablo III Overture," high quality song that is purely Diablo. In fact, I'm listening to the track as I write this news post, and it's taking me back to the good old days of Diablo II. So, pick up the music file. Sure, you can only get it via iTunes, but where else are you going to find a great piece of music for free (well, legally, that is)?