In the even that a U.S. citizen's digital device is lost due to theft, loss, or damage, the NSA will allow us to use the NSA copy of our hard drives/memory cards/cloud-data, in order to restore our lost data to our replacement device.
Additionally, the NSA's copy of our cloud data (email, photos, videos, chats, music, etc) will serve as a backup to the cloud storage of Google, Apple, Microsoft, etc, should their infrastructure suffer catastrophic damage.