Interesting that ten year treasury rate is going down while MBB rate is going up. Normally they move together and allows one to hedge one's portfolio of mbs's by betting against treasury's. What's happening now is that NAV is going down and is not being offset by the hedges. Are there margin call issues here? If so, then the first one out the door (by selling mbs's) wins, or at least, preserves the most capital.