I see two possible uses for this.
First, taking the name as indicative of the intended purpose, for backups. In that regard, I consider these DOA, since anyone who can fit their entire life in 300GB can use the cloud easily enough, and those of us who rip everthing we own to a home file server would already require literally dozens of these to store a complete backup. Sorry, boys, but even Grandma has a 2TB drive these days (whether or not she's used more than 2% of it).
Second, and more likely - 4k video. I don't really know where I stand on that one, because on the one hand, even BluRay has more or less flopped (it has made good ground in "replacing" DVDs, but for the most part people won't pay more for BD content); on the other hand, 4k finally represents a serious increase in quality over 480p. I still don't know if people would pay more for it, but having seen a few examples of 4k content on a 4k monitor... Just wow.
Still, if the blanks don't cost $5 each and if the DRM doesn't make these virtually worthless for anything but playing in a standalone player, I suppose these count as a step in the right direction. Unfortunately, with Sony involved, we can pretty much take it as given that they'll blow both those constraints without hesitation.