I don't think there's any need to start praying that it's a total flop. First of all, the prices on the Bitshares exchange don't give the price of BTC directly, they tell you the market price of BitBTC. Then, there's a separate exchange rate between BitBTC and BTC. So even if the price of BitBTC is directly manipulated by some large entity, the exchange rate of BitBTC to BTC will still be able to keep the exchange rate between Bitshares an BTC the same. If the price of BitBTC goes up relative to Bitshares, then either it will take fewer BitBTC to buy a Bitcoin, or the value of Bitshares will fall relative to BTC. Either way, the exchange rate will remain stable.