It is legally a very gray and hard - if not impossible - area to control at this point. The blogs tend to be housed in legal entities outside of the US, and the issue seems to be the concept of someone in essence saying "I keep my CDs here." You can listen to them. You can play them. But if you burn a CD copy you are doing something of legal questionability, not the person who lists it. So there. But, when I ran across the Sgt Pepper multi tracks, I got them. And as mentioned earlier, loads of unavailable stuff is out there. The record companies really are more concerned with Miley Cyrus copies. They are not into Bloodwyn Pig at The Filmore West, or The Jeff Beck Group Live in Miami playing The Beverly Hillbillies Theme in 1968.
And yes, those two are out there.