Speaking of substitutes, Google and Facebook have a strong incentive to squander cryptocurrency. The long vision is a direct threat to the way they operate, and to the very question of whether or not they should exist.
If there was some hypothetical way to decentralize search, email or even social interactions, DLT research is likely the path forward. The whole point is that the nodes cannot trust each other, creating a sort of differential company, where search is provided entirely by those who are searching.
This is vastly different to Google's model which had the ease of assuming that they owned all of the nodes. Perhaps this is why Google and Facebook happened first in human history; they were simpler inventions. I truly believe the decentralized option is better for society, and so it will inevitably exist. Emergent protocols are changing the way I think about how computers talk to each other.