I share some apple lossless. It will show up as m4a but the bit-rate will be greater than 320 kbps such as around 700-800. I know iTunes can uncompress it but I don't know about other programs. So there are 'some' people at least. There's FLAC & APE also but I don't have any of those. And some people share AIFF or WAV. But not too many by the looks of it. As HDD's get larger & net speeds faster the above formats will get more popular.