I mean, it's cool, but somehow it really rubs me the wrong way. Obviously, I'm not going to tell anyone how to use their computing power, but I'm personally contributing to Folding@Home instead.
This is why things like Minecraft and Flash were great, there is a part to the experience anyone can enjoy and accomplish but also the potential for huge depth through learning.
If anything, this project could promote the idea to new crowds, who might end up contributing resources to e.g. Folding@Home.
For instance in LIGO gravitational wave detector one of PhD students accidentally misconfigured one of the black hole-neutron star merger simulation runs, so that it took months instead of days, but resulted in very detailed simulation, which then was used to study fine details of the observed signals.
It's hard to rationalize virtually any notions of conservation (being green, AGW concerned, etc) with this project. Finding the seed of pewdiepie's world is somewhere between absolutely meaningless and completely meaningless.
Just don't comment. Keep it to yourself.
While not as mathematically elegant a comparison, you could certainly run the numbers for gas or any other heating method and find a similar cost comparision. They key point is that a computer heats the way a space heater heats, and heating your home with space heaters is expensive even in spite of the 100% efficiency at turning electricity into heat.