Volunteerism

Admin Gal recently got to 'volunteer' at an event that her corporation was sponsoring.  On a whole, the time was rewarding and fun, aside from the heat and 'glow' that everyone was wearing.
All in all, Admin Gal fully supports corporate events that helps the community and the social causes that the company lives in.  The question arises, is there a line that can be crossed between social awareness volunteerism and brand promotion?  And wherein does that line be come work and not voluntering?
Here are the main points that crossed my mind as I thought about this issue:

1. While most volunteer events and experiences involve work, should the work required really be so closely tied to your actual job responsibility that you feel are working for free?  And should you be?
2. If your company is organizing the event, encourages 'Volunteers' to man every conceivable booth, gate, and other event staffing need, shouldn't they be paying employees for the time instead of taking advantage of a 'service opportunity'?
3. The guise of 'volunteerism' should not be code for promote, promote, promote the company while giving it a glaze of social relevance.

Admin Gal is aware that most corporations have parts of their companies that are devoted to the concept of 'doing good for the community'.  But at some point, what the employee does during this time really does have to benefit the community, not the corporate coffers.