People with runaway egos often are in denial about their behavior. They see themselves as tremendous employees or managers with few, if any, faults. The result of this type of attitude is resentment from fellow employees. Employees will be less likely to open up to the ego-centric employee and will often try to undermine them or work against them to show them up. Ego can have a devastating effect on team work and productivity.
Big egos can lead to lashing out at employees to make a point.
And the ego can force managers and owners to make decisions that feed the ego. Those decisions might be good for the individual's self-image, but bad for the business in some way. Take a look at your ego. If you have been told that you are arrogant or stand-offish, try to change the way you come across to others. Take an interest in others.