People have wants and needs that are unmet. If you are lying in bed, eventually you are going to get thirsty. If you dont act on that need, you will soon begin to feel discomfort, and that discomfort will motivate you into action.Once your basic needs are met, you will move on to satisfying less immediate needs, like paying your mortgage and saving for your kids college fund.
These needs and wants should not be mistaken for demand, as it exists in economics. How you choose to satisfy your needs determines what your demand is. If you are thirsty, you might just get a glass of water, or you might head down to a pub for a beer. If you are lonely, you might see someone in person, or you might go on Facebook. Walking out to visit a friend doesnt show up in aggregate demand statistics, even if that perfectly satisfies your need for companionship. If, on the other hand, you browse Facebook and play a few games, ad revenue is being generated, and this economists can measure.
Its silly to think that, before MySpace and Facebook appeared, there existed a consumer demand for websites that let people post pictures of their pets and describe what they are doing at that moment. Its just that the founders of Facebook found some human wants to satisfy, and came up with a way to monetize on their ideas. Orkut, Googles social network that appeared in the same year as Facebook, did not thrive, and eventually shut down. Presumably, this service might have satisfied consumer wants, but Facebook offered a superior service, or marketed itself better, or both.