On incentives...
If you take seriously Daniel Krawisz's point
here, it starts to become clear that none of the parameters in the Bitcoin protocol are anything more than first approximations. As the protocol runs up against real world use cases and limitations, some things will have to change. It sounds scary, thinking that even the coin limit could change..."What about hard money?" Here's the thing: Bitcoin is always at the mercy of the market, it is always controlled by the market, always shaped by the market. Sure the presets matter, they function like Schelling points and the market is wont to change them lightly. But it will if absolutely necessary.
As gold's price history shows, "hard money" is still always subject to the market. If the market decides Bitcoin needs 23 million coins instead of 21 million, it will be done. You can keep your coins on the original 21M fork as their price plummets because, ex hypothesi, the market only endorsed the change if it was absolutely necessary, meaning the old fork is pretty useless. Most like this will never happen, and for the very reasons that we wouldn't want it to happen. But it could, if and only if circumstances are so dire that it *should*. None of this should be disturbing, though, because almost everything in our lives already depends on the market. People don't push you into traffic, even though they could. The free market doesn't price for your daily necessities at tens times more than usual, at least without a damn good reason that you would ultimately agree with.
Bitcoin will be restructured as necessary to make it work, to preserve the value of the
Universal Ledger of Civilization at all costs. Because that's what the market wants. Insofar as that means no change, it will undergo no change; insofar as it means change, there will be change.
Every classic document of Voice and Exit references this reality. In the Declaration of Independence it says, "Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes." This is analogous to the fact that the market will not readily deviate from what was set in stone by Satoshi at the start, but that this should not be mistaken for an absolute guarantee. The market simply guarantees that changes will only be made when they are beneficial, according to the wisdom of the entire investing population weighted by those best understand it, which has the legendary accuracy of a prediction market (for example, in 2012 the Intrade prediction market correctly predicted 49 out of 50 electoral outcomes in the US states).
Hence really taking Krawisz's point seriously, considering all its ramifications, we find that Bitcoin is solely controlled by the market, and will be whatever the market deems most useful, with the initial presets as only one factor, albeit an important one. We haven't seen this come to the fore yet simply because the limits of scarcity and so forth have not yet been approached. As rubber meets road, more and more this way of thinking will become critical to adopt. It will confuse and disturb many, but really we have all been at the mercy of the market all along, and this is just the full revelation of the extent of that reality.
In the case of full nodes, for instance, any changes that may be necessary to incentivize them will be made, if and only if needed. Nothing is
really set in stone: it is better than set in stone; it is maintained by the wisdom of the market, even the wisdom to guard against the vicissitudes of temporary market swings by reacting with appropriate ponderosity, except in a true emergency when the change can be lightning fast. There only need to be infrastructural changes to enable fork arbitrage on exchanges so that the market can work with minimal friction when the time comes. And probably these infrastructural changes will not be made until a small crisis has forced them. Antifragility works in this way.