Wow, another very interesting thread.
I believe giants existed because the Bible says so.
This is where as Christians we have to be a little careful. If we go around talking about giants, the world is going to think we are very silly, superstituous people. Even some fellow Christians think that. But the truth is, there is much scientific evidence that very large people lived in the past, as shown in some of the articles and photos here. As Christians we never need fear true science, because true science will always agree with God's truth in the end. It is false, psuedo-science we have to fight against.
I have never quite understood why, but evolutionists do not like the idea of giant humans and usually try to discredit serious findings of evidence.
Who knows?, maybe someday they will find Goliath's remains, it ought to be pretty easy to identify him with that stone stuck in his forehead.