I know that people can use IPFS to voluntarily pin data so that it is redundantly hosted, but supposing there's some paid service that goes with that data, I don't think IPFS helps identify the users that have been pinning the data so that you can offer them the service for free.
In theory the users could just mine filecoin and pay for the service in that, and then I could dispatch storage contracts to the users in ways that ensure that the entire dataset stays pinned, but so far as I know that's not built in. Besides, a spare phone isn't up to the task of mining filecoin (you need a pretty beefy rig).
I think it would be cheaper and simpler to keep the "have you pinned enough data to justify a free premium account?" Logic all together in one place and not introduce the mining process as an intermediary, but not so cheap and simple that every app that does it should have to implement it themselves.
In theory the users could just mine filecoin and pay for the service in that, and then I could dispatch storage contracts to the users in ways that ensure that the entire dataset stays pinned, but so far as I know that's not built in. Besides, a spare phone isn't up to the task of mining filecoin (you need a pretty beefy rig).
I think it would be cheaper and simpler to keep the "have you pinned enough data to justify a free premium account?" Logic all together in one place and not introduce the mining process as an intermediary, but not so cheap and simple that every app that does it should have to implement it themselves.