Ok it might not be yet, but things are changing rapidly. In Germany, established parties are running scared right now over loosing first-voters, and push for significant change.

Imagine a little icon or traffic sign or so we put on websites informing users about independently measured power effiency. Could work with privacy and network footprint as well. Hell, maybe I should put up a competition for graphic artists to design such a thing, with a 1k USD/EUR prize.

Are you saying there's no feedback in the sense that a website that consumes more resources costs more to the owner? I would have thought there is.

I'm afraid I've not completely understood. I was talking about the power consumption for the users of the site/webapp rather than the power necessary for running web servers. But that would indeed be another important measure (and I believe power density is certainly on the radar of data center equipment buyers, but not framework users and most developers yet).

I wouldn't rule it out. Considering the occasional tech-related hysterias, all it would take is for someone high profile to start complaining about how much power and heat slack generates.