Currently, IPFS has two classes of services and two corresponding incentives, neither of them directly involving payment.
- Users host content because they want to make it available. Either because they care about the content, they care about the health of the network in general, or they’re being payed by some third party (pinning services).
- Users answer metadata queries mostly due to inertia and/or altruism. IPFS nodes will store/serve metadata (which peers have file X, where can I find peer Y) by default. At the moment, the cost of doing so is minimal and even if users start turning this feature off, the network doesn’t really require that many metadata (DHT) nodes to function (paradoxically, it will likely get faster with fewer DHT nodes). If it really becomes a problem, we may need some incentive system but we’ll cross that bridge when we get there.
However, we’re also working on a project called Filecoin that will have a direct incentive (payment) system. One of Filecoin’s goals is to be the definitive answer to “how do I pay to store content on IPFS”. You can find a discussion of the incentives in the Filecoin whitepaper.