From tha archives, "J" was only supposed to be at NSI for a temporary period before moving to a different location (and organization), much like "L" and "M" moved to LINX and WIDE after a brief period at ISI and NSI.
The real question isn't why "J" has moved a few miles to a different Verisign building, but where in the world should "J" move?
From my limited understanding of the data, Hong Kong appears to be the most technically sound location for a new root server. Asia-Pacific rim is heavly dependant on "M" now. Yes, a lot of A-P traffic is exchanged on the west coast of the US. But HK is probably the second most central telcomm location for the regiona. South America, Africa, Russia, India have lots of people, but aren't very central network-wise. Root servers need to be able to serve the world, not just a local region or country.
patience grasshopper. :) pushing "J" to a distinctly different broadcast domain is the first step to pushing that instance elsewhere. pre-ICANN, things moved fairly quickly as compared to post-ICANN. --bill