Having an agreement in place is a wonderful thing, but how could you ever guarantee that everyone who had access to it would honor that agreement? In the YouTube era, keeping something as rare as a Mary Heiny video off of the 'Net would be nigh impossible.
In some ways I hear echos of the argument that the file sharing proponents have with the record industry in this conversation. We have on one side the idea that she and teachers like her are an invaluable resource whose knowledge should belong to the aikido world as a whole because of her direct link to O Sensei. But on the other side we have the fact that she (and other teachers) has devoted herself so completely to teaching that she has no other source of income. If she were raking in the money like the big rock bands and if she were charging an arm and a leg for seminars, I might tend to side with the argument in favor of free public access. However, as her current situation with the hip surgery shows, she's not. To post her material on the net could do significant damage to her ability to make a living which IMHO is completely unfair. Even worse, if her ability to make a living teaching is diminished enough she might have to turn to a different profession, which would be a very grievous loss for us all indeed.
Here's hoping the surgery goes well. Perhaps someone could talk her into creating a personal archive of material to be shared either after her retirement or after her passing?