I often think this is one of those things that can arise in people from both nature and nurture. Everyone lies to a point, but I think how we're raised and taught helps us to draw a line as to where it stops. Some will lie to not hurt others' feelings and some to try and get themselves out of trouble. I think for most people it stops there, because when you go past that point you start to hurt others, either through theft or revenge. There is also a point where I think that some will start to justify their lies when it starts to hurt others, especially if they start to lie too much and get away with it.