Let's take a moment to remember the Nintendo Disk System in which players could purchase new Nintendo Entertainment System games at a discount if they agreed to consume those games via a rewritable disk rather than a traditional cartridge. Nathan White over at Retroware TV has taken a look back at the system, its legacy, and how it ultimately fell apart.
It is, unfortunately, this precise ease of rewriting the Disk Cards that ultimately contributed to the demise of the console. Certain types and brands of 3.5″ floppy disks, including Mitsumi’s own Quick Disk could be modified to work on the Disk System, and piracy predictably ran rampant. Piracy was such a problem, in fact, that plans for a North American version of the Disk System were ultimately scrapped. This directly lead to the development of the in-cart battery back-up save feature that debuted with the North American release of The Legend of Zelda. The Nintendo Entertainment System (as it was released in North America) was in fact originally designed to connect with this undeveloped NTSC version of the Disk System, as evidenced by the parallel port in the bottom of the console. This was meant to communicate the Disk System directly with the NES’s motherboard, eliminating the need for the RAM adapter connection in the cartridge slot that was necessary for the Famicom Disk System to function.
While the technology is certainly neat, I think we ended up with the better end of the deal in North America, Europe, and beyond with battery-backed memory for saving game progress. Sure, those batteries are dying off now, but at the time it was really so much more convenient to not have to deal with rewritable disks for maintaining accomplishments and storing games. While it would have been interesting to see the technology in play elsewhere, piracy would have certainly diminished its impact across the rest of the world. It's a shame how the human factor can ruin a perfectly good product idea.