If you are not paying to be a "Premium" member, you are limited as to file size and total storage space. MP3s allow people to play the song on the BM player, any other format doesn't, it can only downloaded (if you allow that- its a setting).
My reverbnation site: http://www.reverbnation.com/mikebirchmusic
Youtube: http://www.youtube.com/mikebirchmusic
Facebook: http://www.facebook.com/mikebirchmusic
Youtube: http://www.youtube.com/mikebirchmusic
Facebook: http://www.facebook.com/mikebirchmusic
