Certainly it does.
You could probably consider both Carl and David to be speculators in the scenario.
The price is set by a seller and a buyer both being willing to exchange at the same price. It doesn't matter if the reason they are buying or selling is to speculate on future prices, to buy something from SilkRoad, or to pay an electric bill. If they have a specific price they want, then they place a limit order. If they just want it now at the best price anyone is offering, then they place a market order. If there is a bunch of selling wanting an immediate sale, then they take up many of the pending "bid" offers driving the exchange rate down. If there is a bunch of buying wanting an immediate purchase, then they take up many of the pending "ask" offers driving the exchange rate up.