I fail to find the significance here. The most environmentally friendly option would be not to own or use any hard drive. Or at least a flash drive? And doesn't Windows already have power saving modes for hard drives (I know they spin down when not in use for a while)? And does this really save that much power when compared to that?

Perhaps some power usage stats/comparisons would make this less vague...

The most environmentally friendly option would be to live in a cave and catch/grow your own food. However, since we're technologically beyond that ...

Windows does have the option to spin down the HD when the computer (as a whole) has been idle for the set amount of time. However, if you use this HD for MASS storage of files that are accessed semi-regularly, the power save feature is very nice. This means that the drive itself knows that it's not being used and will go to sleep, even when you're using the computer.

Sure, flash media is more effective, or even pressing the power button on the HD. What if you want to connect this to your WRT350N and have your router serve the files to your network? Well, then the power-save feature is ideal, since you would have this in an "always on" state. The drive would decrease power consumption when activity is idle, but you wouldn't have to walk into the other room to to turn your HD on with your wireless network configuration.

What if you hack the firmware with DD-WRT? Then you can VPN into your network from across the internet and still access your files, because the drive will "wake up" when you access it.

Personally, I'm keeping an eye on this drive and waiting for the capacity to hit something like 1TB.