First, let me say that I like Ser Jorah Mormont. He's an intriguing character. He's a good fighter, he's endured some hardships, and he desires to do good. He has a tremendous amount of knowledge of history and battle, but little practical wisdom on morals. In the end, Jorah is a bad man.
He spent his family's treasury on vanity. The finances that his father left him were wasted. He was unfaithful to his predecessors and to the family that would rule after him.
He broke the law by selling poachers into slavery. No matter how much Jorah wants to, he cannot rationalize his actions. All guilty men in the Seven Kingdoms are given a chance to take the Black before being sentenced... this is the one chance these men have to redeem themselves. Perhaps the poachers were not worthy of the chance for redemption, but that is not for Lord Mormont to decide... the law comes from the King. And all justice is provided in the King's name. When Jorah sold the men into slavery, he was selling them in the King's name. Jorah's crime was that he misrepresented the King (and by chain of command and authority, he misrepresented Lord Stark also) to his people. Misrepresenting the King's name is more than unfaithfulness... it's treason.
Later, Jorah abandoned Viserys, his sworn Lord and King. Treason. But Jorah did not see it that way because he was already secretly working for Varys.
Later still, Jorah accepts Varys' offer (money for spying and pardon for killing). He pretended to serve Dany, but he was serving Robert. He laid his sword at Dany's feet and she granted him title and office. When she found out that Jorah was spying for Robert after she had accepted his service, she should have given him to Belwas. Again Ser Jorah was guilty of treason, but he did not see it that way... in his mind he'd abandoned Robert for Dany. He thought he'd betrayed no one, when in fact he'd betrayed both Robert and Dany.
Jorah is faithful only to himself. He switches allegiances like Arya changes names. He's betrayed everyone.
