Communications of the ACM CACM Volume 61 Issue 6, June 2018 doi:10.1145/3208095 Nicholas Weaver Peter G. Neumann Inside Risks -- Risks of Cryptocurrencies Considering the inherent risks of cryptocurrency ecosystems. PDF <http://www1.icsi.berkeley.edu/~nweaver/papers/cryptorisks.pdf> <https://dl.acm.org/citation.cfm?id=3208095&dl=ACM&coll=DL> Cryptocurrencies, although seemingly interesting idea, are simply not fit for purpose. They do not work as currencies, they are grossly inefficient, and they are not meaningfully distributed in terms of trust. Risks involving cryptocurrencies occur in four major areas: technical risks to participants, economic risks to participants, systemic risks to the cryptocurrency ecosystem, and societal risks. Fortunately, for all but the last case, there is little risk to anyone not directly participating; []