Freedom of the press
The Illinois High School Association (IHSA) has banned media photographers from championship games, unless the media sign an agreement not to sell pictures taken at these events.
IHSA grants exclusive photo rights to selected vendors and is determined to protect its business contracts. Its policy has prompted a legislative call for an audit of IHSA finances.
Major League Baseball is also trying to restrict access to its games by limiting use of photos by online news services and bloggers, according to the Chicago Tribune.
Don't try to enforce policies like these at your event. The more people who can see or read about your event, the better. You can certainly hire a company to take pictures of finishers and award it exclusive rights to mail sales info to each runner (you provide the mailing list).
But allowing a photographer from the local paper to sell a picture to the parents of the winning runner, for example, won't hurt you race. Trying to stop the sale, on the other hand, will anger the runner, family members, friends, and those who feel the first amendment rights of the photographer are being trampled.
And it will make your event appear greedy and petty.
There are a lot of ways to make money from your event. You don't have to squeeze every last person out of the picture.