Fair enough, but you do realize that not everyone will optimize inner loops after switching to C/Java? Certainly not to the extent of scientific computing or even the language shootout snippets.

Also to address the power usage of one server. The 6.6 tonnes number seems to come from having the server drawing 1kw of power continuously for an entire year. The biggest server I could find on Dell's site (E910) comes with a 1.1KW power supply. This DOES NOT mean that it draws 1.1KW continuously. Indeed, outside of peak usage hours it probably draws much less. This is amortized over many users as well. Even slow, interpreted languages can serve hundreds of users on such a server.

Compare this to driving 10 miles/day in a medium-sized car. This produces 2 tonnes of CO2 annually, and unless you're diligent at carpooling, probably serves one person. Even a small car will still use half of that. If some new software helps even a small number of people telecommute instead of driving, the result is overall positive. For this to work, such software has to be cheap (certainly cheaper than driving) and for that to happen programmer time must be conserved.