I wonder to what degree FAI/CEV engineering considerations overlap with cryptocurrency/efficient-market engineering considerations. If they are a close match, encouraging the development of the latter would have benefits for the former, and could even be essential to overcoming scaling problems (since FAI is harder to sell investors on than cryptocurrency).

This isn't just a random idea; markets are how humans in the absence of superintelligence actually do try (with some, not-unlimited success) to implement their values. Prediction markets are a possible extension of this concept, but even your run-of-the-mill securities markets are reliant on various kinds of predictive logic that responds somewhat to human desires and needs.

Not trying to trivialize the AGI field since it is outside my specialization, but is there some not-terribly-unlikely way in which a really good cryptocurrency could basically be/evolve into the same thing as an FAI? If so, are there any particular properties that would be likely to nudge it in that direction / away from uFAI?

I'm kind of concerned because I see bitcoin (and/or anything sufficiently similar) funding competition to purchase obscenely large amounts of hardware -- which could possibly even extend to the point of satellite arrays that harvest solar energy, and space based fabrication of new ones. If it gets to that point, we might end up with a Dyson sphere that basically does nothing but compute bitcoin hashes. Extraordinarily wasteful, but not necessarily catastrophic for existing humans if the network continues to recognize them as owners/controllers of the resources in question.