Is Shyness a Vice?

Had a student raise this question with me the other day. In our culture, we reward the extrovert. Putting yourself out there is seen as evidence of substance of character. The great individual is the one who acts, not who watches. Be a leader, not a sheep. Being reserved and quiet is only acceptable if it is done in the Dirty Harry, strong, but silent, coiled snake, ready to strike-type way. We treat boldness as intrinsically good, but is it? Does the shy person lack a self-confidence that one should have?

While there is certainly pathological shyness that will keep one from doing what it is that needs to be done, we're talking here about being a garden-variety introvert who just avoids calling attention to him or herself, who doesn't like the limelight, who does not seek attention or leadership roles. Do people who are shy need to learn to get over it for more than pragmatic reasons? Is there something that diminishes you as a human being for being shy? Is shyness a personality flaw?