Ultimately, we’re all social beings, and without one another to rely on, life would be not only intolerable but meaningless. Yet our mutual dependence has unexpected consequences, one of which is that if people do not make decisions independently — if even in part they like things because other people like them — then predicting hits is not only difficult but actually impossible, no matter how much you know about individual tastes.
The reason is that when people tend to like what other people like, differences in popularity are subject to what is called “cumulative advantage,” or the “rich get richer” effect. This means that if one object happens to be slightly more popular than another at just the right point, it will tend to become more popular still. As a result, even tiny, random fluctuations can blow up, generating potentially enormous long-run differences among even indistinguishable competitors — a phenomenon that is similar in some ways to the famous “butterfly effect” from chaos theory. Thus, if history were to be somehow rerun many times, seemingly identical universes with the same set of competitors and the same overall market tastes would quickly generate different winners: Madonna would have been popular in this world, but in some other version of history, she would be a nobody, and someone we have never heard of would be in her place.
Even if you think most people are tasteless or ignorant, it’s natural to believe that successful songs, movies, books and artists are somehow “better,” at least in the democratic sense of a competitive market, than their unsuccessful counterparts, that Norah Jones and Madonna deserve to be as successful as they are if only because “that’s what the market wanted.” What our results suggest, however, is that because what people like depends on what they think other people like, what the market “wants” at any point in time can depend very sensitively on its own history: there is no sense in which it simply “reveals” what people wanted all along. In such a world, in fact, the question “Why did X succeed?” may not have any better answer than the one given by the publisher of Lynne Truss’s surprise best seller, “Eats, Shoots & Leaves,” who, when asked to explain its success, replied that “it sold well because lots of people bought it.”
Go read the whole thing (it's not that long).