Storing in the cloud makes sense for music and other stuff that’s been published, but he should be taught from a young age that personal info stays personal. And slapped down hard if it doesn’t.
Cloud for personal info = privacy theft. Once it’s out there, it’s not easily removed.
This being said, I use basically no cloud services other than e-mail (buy CDs or download my music directly), and 16GB on a smartphone is plenty for me.