Is a dystopian future plausible?

There is heated debate about the relevance of the dystopian novel in recent times. Some argue that big brother is but a generation away, while others say that without the invention of a suppresant (Huxley's "soma", for instance) mankind cannot be subjugated. What is your opinion on the plausibility of a dystopian future? If it is plausible, what are some requisites that need to be fulfilled, and how so?