Putting on my "green" hat:
Hey, we're starting to be forced to move away from gas guzzling cars, maybe we should be moving away from inefficient speakers and power guzzling amps as well?
I say this being a very proud and happy owner of some fairly inefficient yet great sounding speaks (the Ohm Walsh 5's) and an amp (MF A3CR) capable of driving them very nicely to reasonable SPLs in my listening room, yet I know that a bigger, beefier amp could up the SPL ante further if desired!
Class D amps seem to be a step in the "green" direction ie higher efficiency and lower power consumption to power our gas, I mean watt guzzling speaks, like my Hummer-like Ohms!