[troymc]

One of the central assumptions in the argument is that the miners need an economic incentive, a (spendable) reward for mining.

How then to explain why people contribute to Wikipedia? Or volunteer at the local seniors centre? Or donate compute time to SETI@home (and other BOINC projects)? Or add map data to OpenStreetMap? Or test open source software? Yes, some of those people get paid, but many do not.

The incentive need not be economic.

[FBT]

Say what you like, there is an incentive in the opposite direction in the case of a blockchain used as a trust-store, which does not exist in the other cases you described. One could make a lot of money subverting a trusted blockchain, whereas Wikipedia vandals don't profit a cent.

This means that you will inevitably have massively funded efforts to subvert such a blockchain. One thing I know for sure is that simple financial self-interest is one of the most powerful things in the world. Every blockchain has that fact working against it. The reason they don't collapse is that on the other hand, they have that same force working for them as well. A volunteer blockchain like you propose wouldn't stand a whelk's chance in a supernova. Sorry.

[bhouston]

None of your examples are in regards to for-profit endeavors. Thus while you are correct that some foundations that are good causes can get people to contribute out of their own good will, this doesn't suggest that novel blockchains by for-profit companies will attract good will contributors.