I believe the young earth creationists are wrong because of the Bible and science. I believe that God left geological, anthropological, and various other types of footprints when guiding his creation's development that scientists just recently have come to understand as the various stages of "evolution." Of course, without any supervising intelligence, I think evolution has a few logical flaws (ex nihilo, for one), but I see no reason not to believe that God directed nature's progression, the crowning result of which was humanity.
Think about this - in Genesis, God is said to have brought forth all nature in various stages, and then what came after all the other lifeforms? Man! That's just what scientists say happened, except that many don't believe there was an intelligence supervising this process.
Besides that, because I trust the Bible and am convinced of its value, I'm not content to simply accept the first thing I think it says. In my occidental worldview, it seems logical that all narratives in the Bible should be historical (unless labeled otherwise). That's all very scientific, because we're scientific - that must mean we speak God's true language - right?? How presumptuous. Everything we know about the contemporaries of the Hebrews tells me that they just didn't think the way we do about history and such all the time. They saw truth in legends, myths, and parables, and felt guided by them. Why should God speak to the Hebrews in any other language but their own?