20 years ago....
20 years ago, the lasers and mirrors required meant while the medium was small, the read/write apparatus was humungous. This was because lasers were more difficult to make, and there was presumably significant power loss in the medium.
There have been many incremental improvements since then in both media and laser tech, so I'd guess that it's on the cusp of being a commercially viable technology. The last attempt to produce something was a disc, and aimed at the removable media market, and that introduced certain engineering complications.
These guys have a better chance, as they'll be aiming at the fixed-drive market, and now's a very good time for that, as SSDs have opened the market to non-disk-based systems. It also plays to the miniaturisation trend even more than SSDs - if they can get the power requirements low enough, the next-gen iPod won't only be able to hold your entire CD collection, it'll be able to store your entire DVD collection too... and perhaps even without any additional compression.
Put this in an Android phone and the era of the truly universal personal portable computer will begin, and office desks the world over will have mobile phone docking stations instead of PCs or laptop stands.