[freejack]

Directors solely have a responsibility to the corporation. The corporation has a responsibility to the shareholders.

This gets mucky on boards of publicly traded boards because large shareholders can be directors and may have divided loyalties. There are strong conflict of interest policies, requirements of care and so on that are intended to help manage this, but it can be a tough balancing act.

Wikipedia has a good outline on director's duties. If you plan on leading a successful startup, learn this cold. http://en.wikipedia.org/wiki/Board_of_directors#Duties

I've served on corporate boards and it can be a tricky place to serve in the interest of the organization, balance all of these requirements and stay true to your own personal sense of purpose. Its also very rewarding work and I recommend it highly to anyone that has the opportunity to participate, even for smaller organizations, non-profits, etc.