I say this half flippantly and half seriously. :-)
If there's something else each person has a finite amount of that we could count for one-person-one-vote, I can't think of it. IP addresses... much easier to get lots of them than CPUs.
If I were you, I would have considered a mapping that included, "For each entry into the bitcoin transaction recording/gold mining lottery, please send $10 to Satoshi."
That would discourage botnet operators from thousands of nodes. And if it didn't you would have tens of thousands of dollars! ;-)
I can't imagine a more splintered network.