Poloniex seems to be the exchange with the largest volume (I somehow doubt anyone is buying long-positions larger than that) - so it looks like they could at least cash out several thousand bitcoins - although it's been a while since I've been on their site and if they offer API access some of those positions might be automatically diverted as the price moves.

[0] http://coinmarketcap.com/currencies/ethereum/#markets

[1] https://poloniex.com/exchange#btc_eth