It's in the far distance but I was thinking about this today too, the problem of spam. For this platform, you could make a scale for the expiring of the data based on how much it was tipped, this would put garbage sooner in the bin.
And I saw crossposts from Hive blockchain blogger today first time here. That one was a little more stimulating. I figured out that if you could anonymously pay for hosting of posts and associated media, and tips paid to hosting nodes, you could dispense with the centralised web page and switch out to an IPFS based feed and spam simply would fail to be funded and be deleted when space is needed.
All it requires is a payment/hosting protocol, and the one I'm building for indranet would so easily be extended to support this.
When I have the payment system working maybe I can get someone to build a service that binds to an IPFS node to enable renting storage for time on IPFS pins with anonymous payment, and later, can be anonymous upload when I get the routing working.