The concept of loyalty is an important part of ethics. Plato originally said that only a man who is just can be loyal, and that loyalty is a condition of genuine philosophy. The philosopher Josiah Royce said it was the supreme moral good, and that one's devotion to an object mattered more than the merits of the object itself. Loyalty is a quality you look for in a friend.
Betrayal is the breaking or violation of a presumptive social contract, trust, or confidence that produces moral and psychological conflict within a relationship amongst individuals, between organizations or between individuals and organizations. Often betrayal is the act of supporting a rival group, or it is a complete break from previously decided upon or presumed norms by one party from the others. Someone who betrays others is commonly called a traitor or betrayer.
all of the above was taken from wikipedia. i'm too upset right now to elaborate whats going on in my head. will check back later and update.