I personally know someone who gave a two week notice at Amazon and had his manager ask him to stay out the quarter. It's all about relationships and reputation. People with a proven track record of quality work and strong ethics are valued there.
Nothing. Relationships are by definition bidirectional. Being able to have a good relationship with a manager implies that that manager is at least not awful, and most likely also good. The person I refer to would never have delayed starting his new job as long as he did if he didn't have professional respect for his manager.
