I do know the ReadyNAS does specific tweaks to the Green drives, in line with what Mark Lord advises. And I haven't seen mass failure stories about the Green drives on the ReadyNAS forums. It's possible the Drobo doesn't do anything special, leading to the issues the Ars person saw.

I've run desktop/green like class drives in all 3 of the ReadyNAS units I've had with no major issues. Each time, I just make sure the drive is on the compatibility charts. Just a failure here or there within normal. I do avoid Seagate now, but purely based on their lack of advanced replacement for failures now.