Many books, typically fantasy genres, have dream sequences. The reasoning behind the dreams can be used for different purposes, such as a premonition of what is to come. Others show the deeper feelings someone may have about a situation going on in the book. Sometimes, these dream sequences can push a reader out of what is believable given the setting of the story. Each person has their own view on what dreams really mean, whether they be the random firings of your brain during REM, the ability to tell the future, or some meaningful analysis of how you really feel. Someone who sees dreams as a way for the brain to keep you occupied while you sleep using jumbled together memories to create an environment may only accept the idea of dreams being clairvoyant in a fantasy setting. An author who sees memories as being clairvoyant may have that kind of dream sequence in a "normal" setting.
For the author, thinking about the reader may be difficult. While it it not assumed that an author should please anyone but himself, the very point of the dream sequence has ruin a reader's experience. There must be a point to the dream sequence, and if there is not a strong enough case, an author must consider removing it from the story, or conveying what may be important in another way. So far, I have only used a dream sequence once, in "Survival Tautology" to show the mental impact of what a person has gone through after living in a world full of zombies for so long.