Check out the six pages of license agreement for tickets for Vancouver 2010 Winter Olympics.
Amongst a whole raft of prohibitions "...Ticket Bearer [shall not] engage in political, commercial, advertising or other promotional activities. Ticket Bearers may not ... wear or bring political, advertising or other promotional or other commercial items or clothing into a Venue. Entry to a Venue will not be granted to any Ticket Bearer who is wearing or carrying any form of political, commercial, advertising or promotional message. Religious and racial propaganda and demonstrations are prohibited inside or in proximity to a Venue perimeter. Violators will be subject to removal from a Venue without a refund... prohibited items and activities : smoking, broadcasting or recording through the use of cellular phones...strollers...food and beverages...prescription-strength medicines...banners, flags... signage of any nature, skis, snowboards, bicycles, balls, Frisbees, helmets (e.g., motorcycle, bicycle, sport, etc), and noisemaking devices..."