Here's one of the dirty little secrets of corporate brainstorm sessions: When they are led by upper management, department heads, or project leaders, they usually get manipulated.
Because honchos and honchettes are so heavily invested in the topic being brainstormed, it is common for them to bend the collective genius of the group to their own particular point of view. Not a good idea.
Participants -- out of respect for the expertise (or position or parking space) of the facilitator -- will invariably moderate their input. The results? Same old same old.