I'm a little baffled as to why they would discontinue (in my opinion) their best color, yet continue to keep colors like Brilliant Green and Brilliant Red. I'm sure they have their reasons, but still, it's a mystery to me. So go out and find this ink wherever you can if you want it, because the only ink that exists is what's currently on retailer's shelves.
**5/22/11 update- this thread on FPN was started as a result of this announcement, and it seems the reason for the discontinuing of the ink in the US may be because there is a chemical in Blue-Black that is not in compliance with US TSCA (Toxic Substances Control Act) regulations. I have no idea what is in the ink or why all of a sudden it's not in compliance, but that is what at least one FPN member seems to have discovered from her investigation.