I think it was either Google Play Music or Amazon (maybe both?), where you could upload your own music in order to stream it to any of your devices. Some felt it was questionable because they could replace what you uploaded with the same tracks from their existing library of music available for streaming or for sale. I understand why--it saves them storage space. I guess for casual listening it wouldn't be a problem, but someone who had a rare version or a different mastering would be disappointed to find it had been replaced.
I have a few of those in my Amazon account also, although lately it has mostly been vinyl purchases (which are also eligible). Some records also come with download cards--Peter Gabriel does it right and offers high-res downloads, not MP3, so at least we have the option to downsample and burn to CD, or convert to WMA or MP3 (or whatever else we'd like) for portables.One thing I have noticed lately is that if I buy a cd I usually get a free download of the mp3. I haven’t used it much but I have a sort of library of those in Amazon. Probably should download those and load a flash drive.