Google will have the same problem as Microsoft in this area, lack of a consistent platform and user play-back device. I think that Apple's success rides on the fact that they control the entire pipeline (sans content creation) and provide the user with a consistent and simple interface, with relative freedom for the user to listen when and where they want. I think that any other distributor will have a problem if they do not control or at least have a very strong influence over the distribution and play-back pipeline.