The idea is that some fraction of users will be configured to reshare content, which helps distribution for popular content scale. This seems to work in practice for bittorrent.
Yes, but only for suitably popular content, as all the dead torrents will testify. This doesn't make IPFS very appealing to Joe Blow, content maker unextraordinaire.
Regardless of whether I think this is a bit of a far fetched use case or not, this really does nothing for Joe Blow and his content distribution needs.
But let's roll with it anyway. How does IPFS solve this problem, and more specifically how does IPFS solve this problem any better than just publishing a torrent of Joe Blows collected ramblings?
I don't think that word means what you think it means.
Asking what problem a technology solves is a very practical question. Countering with "IPFS is a nice and fun technology", is the very opposite, i.e. alluding to that there might be some theoretical benefits to it, but that your mainly into it for gits and shiggles.
ZFS is less flexible in deduplication because it's not true content addressing, and git has lousier protocol. Rsync and unison also have lousier protocol and don't deduplicate storage.
You still have to serve the content from a server, since you cannot depend on the kindness of strangers to persist your content.