It's a good concept for people that travel a lot and do not want to use a ton of data to stream content. But for an every day case I do not see it as useful. Unless someone uses their phone as their only device. But as said above. You could use a ton of different services to store your data
That's my thing, plus if you're planning to upgrade (or have an upgrade available) it's stupid to buy the case for a phone you're only going to keep for a year.