Blockchains can be used to create a decentralized storage marketplace. Data is not actually "stored" on the blockchain – it is stored by distributed hosts – but the entire marketplace is managed by a blockchain.
And how does the timestamping that blockchain provides help in managing the
storage? To me it still looks like a job for a DHT. The only thing I can think
up is that the registry of files is replicated in the whole through the
blockchain, but then it needs a ton of excessive work just to put a timestamp
that will not be used, and the whole system would be better off with
a gossip-based registry replication.
The blockchain is used to create storage contracts between renters and hosts, and send payments to hosts.
Oh, so it doesn't concern data storage in particular, is as relevant to
storage as to distributing excess of turnip.