Cloud storage is useful for personal backup, but it's tricky on the millennium timescale of the article since no company will survive very long. If you kept du

Cloud storage is useful for personal backup, but it's tricky on the millennium timescale of the article since no company will survive very long. If you kept duplicate copies at the top N cloud providers at any given time, then you could probably go for 1000 years if N>=3. But this would require an active effort to keep your data alive as companies came and went. A true archival copy can be ignored and still be readable.