I suspect that if N honest backers would expect a net gain from a decision even if they spend X/N voting for it, a single owner of N fake accounts would expect

I suspect that if N honest backers would expect a net gain from a decision even if they spend X/N voting for it, a single owner of N fake accounts would expect a net gain from the same decision even if he spent X voting for it. Anonymity on the internet pretty much inherently means that you can't tell how many actual individuals a given set of apparent individuals really are. You can tell how much money they have (or CPU power, bandwidth, or various other proxies for wealth), but that's about it. I don't see how this wouldn't be an inherent problem for any cryptocurrency (or crypto-whathaveyou-system) attempting to force decentralization (see; the primary actors in Bitcoin split war.)