You're really not that naive, are you? Using your thought processes there would be no market in a stock if a company beat its earnings estimates substantially and said revenues would be up 50% in the coming year. No one would sell. Or if the company tanked, there would be no buyers - as when SOLD made its February announcement, who would buy shares at $14, $13, $12, etc.
But that is why there are regulated markets and MMs. Here's a very simple explanation from a website on investing if you don't know how the market functions:
"If you wanted to buy 1,000 shares of Disney, you must find a willing seller, and visa versa. It's very unlikely you are always going to find someone who is interested in buying or selling the exact number of shares of the same company at the exact same time. This begs the question, how is it that you can buy or sell anytime? This is where a market maker comes in. A market maker is a bank or brokerage company that stands ready every second of the trading day with a firm ask and bid price. This is good for you, because when you place an order to sell your thousand shares of Disney, the market maker will actually purchase the stock from you, even if he doesn't have a seller lined up. In doing so, they are literally "making a market" for the stock."