A participant's perspective
Runners and walkers often don't know - or even care about - the logistical challenges facing race directors. That's understandable.
Registrants, fans, attendees, and customers make decisions based on their own needs and desires, not the concerns of those staging an event, providing a service, or selling a product.
In fact, some runners compete in races as bandits (they don't register) because they don't feel they should have to pay an entry fee to run. Although they enjoy the same course, aid stations, and post-race refreshments as do registered runners, they are not included in the race results. Apparently, that deters many more who might have done the same.
Fun runs, and similar types of events, however, usually can't withhold anything equally as important. Participants are even more likely to expect an event to change its rules to accomodate their needs.
An article in today's Chicago Tribune makes an interesting point about the Chicagoland Bicycle Federation restrictions about Bike the Drive.
Race directors may not face this same issue but they do encounter the same types of complaints. So listen to runner and walker gripes. If you can do something to satisfy those concerns, try.