Why would keeping the sightseers out be a good idea?

How soon should leaders reach out to the community? Can the community provide assistance and help with the emergency management operation? Why or why not?
The community is our customer so we must focus on serving this customer. I have experienced many situations and nearly all of them required us to send out immediate alerts and inform the community. In rare occasions we had to sit on information until we had the facts and could send out the best information and directions. Sometimes if we send information out to soon then the routes in and out of the affected area could become impassible due to the evacuation or curious sightseers. Why would keeping the sightseers out be a good idea?
3.How much information is too much information? How do leaders walk the line of providing details to citizens while still protecting emergency management workers and the community