The safe, reliable answer is nothing. Everysong has a copyright, regardless if your recording has been released or not. Posting it for download without the owners consent violates this copyright.
But, for the most part, you'll only attract problems if you start posting released material that can cost QP actual money right not. If you start posting album tracks, you'll be in trouble. It you start posting long forgotten remixes or average sounding concert tracks, you'll probably be overlooked.
DJ's the man we love the most