On an iPhone you can't bluetooth a song as well, yet it sells like hotcakes. Your argument is invalid, if its based on bluetooth transferring of songs as well, considering that from what I know the majority of iPhone users don't jailbreak their devices.
Besides, Skydrive is essentially a part of the OS anyway. Skydrive is just like dropbox, and its great in a way that no matter how much you download, it won't eat up space on your phone. Its probably not so great for people with limited internet bandwidth I think though. I have true unlimited.