Vore, while sensually satisifying for those who write and read it, demands that, at the end of the story, someone winds up consumed by another animal or person and, more often than not, digested and killed. It runs along the lines of life and death, of morality and vice; this is the danger that it holds.
(difference between vice and sin: sin is the breaking of the word of one's religion, while vice is an act of breaking one's societies rules; often synonymous, but not always)