Should you be disappointed in someone because they did not live up to your expectations? While many in the United States and abroad would say yes, I have to question the wisdom of this. First of all, as unique beings, each of us is a special combination of ideas, beliefs, actions, etc. That being said, holding someone to our vision of them seems somewhat counterproductive. Secondly, disappointment often leads to a change in how you view a person. This can affect love, caring, and understanding on a base level. Ask yourself, do you want to place that much power in an expectation that might have been off base, too high, or even completely unrealistic.
The question then drills down to, if you do not hold someone to your expectations, what do you gauge their accomplishment on? Beyond the question of whether you should be judging a persona all together, my personal view is that you judge them on how they live up to their own expectations. If someone espouses a care for mankind, fair treatment of the poor and rich alike, and caring for the sick/underprivileged/etc. and fails to live up to even a bit of it, disappointment is usually not far behind. Even then, the question still arises on whether or not judgmental attitudes are truly productive to a relationship or the community as a whole.
This also prompts the discussion on self-expectations. Setting expectations for yourself that are unreasonable high tends to lead to a high level of disappointment and self-hate. This is not to say you should not have expectations about your life, goals, path, etc. It means that truth and clarity of vision should start on the internal level first.