Someone who didn't pay the IPO price for the coins.
Who could that be?
I don't think it's even possible. Ethereum is going to start at $16 million capitalization. Where's the ROI? If Ethereum went up 100x in value it would be $1+ billion capitalization. That's compared to earliest people in Bitcoin who saw 450,000 times return. Even today I think there are alternates that will later attain that rate of return. Ethereum is just too big at launch and will fail for that reason.
https://blog.ethereum.org/2014/08/08/ether-sale-a-statistical-overview/
Even on Vitalik's blog he said top 100 wallets control almost half of Ethereum. Wallets are not people. When you invest huge sums you break it up into multiple wallets to minimize potential losses if they happen. Ethereum looks to be a rich man's ponzi scheme (like Mastercoin 2.0) and for that reason it'll fail as there will be no subsequent buyers.