IPFS+Ethereum = incentive. Please do not be so flippant to reject something until you've grok'ed it sufficiently well enough to argue against it. If you have looked at IPFS+Ethereum and found it wanting, I'd love to know what exactly - because from my perspective this is precisely the kind of technology that delivers your stated requirements.
Which is why I find Swarm a better solution. It is literally IPFS+Ethereum with additional support for ENS lookups, deniable storage, redundant storage, etc. This allows for far better privacy and being able to compensate the loss of parts of the file, both features lacking in IPFS itself.
The current swarm testnet performs, as per my experience, better than IPFS in terms of bandwidth and latency.
