I'm curious, why? I havent worked with mainframes for a couple of decades. Is it because they are running legacy apps in Cobol? Or havent they figured out how to parallelize the apps to run distributed? (Going from serial Cobol to Erlang would reduce the hardiest HNer to tears.) Or are they conservative enough to not to want to risk $B if they screw up? I suppose all the govt. failures would be a cautionary tale.