[anjc]

Presumably they're talking about the consumption of Ether as gas, to run contracts. Perhaps they're seeing that algorithmic trading of currency is more predictable than gas consumption by distributed apps, which may be highly and suddenly viral for some period - e.g. Cryptokitties. Viral use of the DApp in theory would increase the price of Ether due to increased demand.

[heptathorp]

That makes sense. It wasn't clear from the paper since they talk about how Ether is "transferred or traded" and comparing it to algo trading.