Russell Cattelan -carbon- computing tax vs cap-and-trade :) 

And JVMs are not soooo bad.  Jonathan's correct that the memory overhead is a bit ugly (48+ bytes overhead for a String in openjdk comes to mind).

And if you want energy efficiency Dalvik does okay.

Me?  I'd just like to find more ways of funding grungy optimization work on the open stack that powers most of the computing grid...