It is amusing the way that music pirates will copy the music but encode it as the open source FLAC before uploading to file sharing sites. Because those sites pay out depending on bandwidth used to download it pays to use the open source FLAC rather than mp3.
Audio encoded to FLAC is typically reduced to a little less than half of the original file size. An MP3, by comparison, is typically one tenth or so of the original file size, but with lost audio information and lower quality. Audacity wiki
Result is the same – stolen music – but open source material helps them “profit” faster.