The interesting question to me is not so much what this means for iTunes, but what does the record industry think it means for iTunes? Three of the big four are selling their DRM-free tracks only on Amazon. Is it pure spite? Do they have promises from Amazon of tiered pricing for the future? Do they think they are going to “punish” Apple and use this as negotiating leverage or drive iTunes into the ground? Or will they all eventually allow the DRM-free versions on iTunes?
For all the noise about DRM, I don’t think enough of the buying public cares that much that it’s going to hurt iTunes significantly. The iPod to iTunes to iTunes Store channel is seamless enough that I think that’s where most of the buying is going to come from, DRM-ed or not.
Tiered pricing may come eventually, but I think non-DRM songs are coming to iTunes first.