I doubt he was thinking flash memory at the time, but 3D storage is already in use. One of the bigger limitations with this is heat, so we have people writing papers like:
I'm not sure if that really counts as 3D storage though. I'm pretty sure that the commentator was referring to holographic storage, which would theoretically have a higher information density, and actually use the third dimension for data storage.
Unless I'm reading those links wrong, they are just stacking flash memory on top of each other. How is this different than finding a way to pack hard drive platters closer together? You're just taking several 2D storage mechanisms and stacking them on top of each other. You're not using the third dimension for anything.
I doubt he was thinking flash memory at the time, but 3D storage is already in use. One of the bigger limitations with this is heat, so we have people writing papers like:
http://scholar.google.com/scholar?q=Thermal+via+placement+in...