A Microsoft file hosting and synchronization service.
Good question Miles. I've been wondering the same thing.
In the past week, I've been in mail and phone contact with Microsoft customer service employees about this issue. As it happens, I've sent them a link to this conversation this very morning. I hope that this will speed things along, but of course there is no way to be sure this goes up the chain form there.
Anyway, should a solution come out of my contact with customer service, I will post it here.