This is the crux of the matter, as others have pointed out. The longer the "boarding" time, the more backlogged you get in triage, until you reach the point where the only patients getting back are the level I/II, and the lower acuity patients are being passed over, with no real way to work them in due to bed space and staff resources. Then you get the LWBS numbers increasing, satisfaction scores decreasing, etc.
The patients get the short end of the stick, with EMS being a close second. My experience has been that once the initial divert domino falls, other facilities begin to follow. I always found it ironic that the hospital could turn EMS away over the radio, but if the ambulance dropped the patient off 1 foot from the door, and the patient simply took a single step forward, the facility would be obligated to treat them, regardless of resource availability.
One of the biggest problems at the hospitals I have worked at is the floor dragging its feet. I know when the ED is busy, everyone is busy, but when you are trying to transfer a patient and the charge nurse says it is going to have to wait because they just got two or three admissions, you just want to bang your head on the table as you look into the waiting room that is currently 100 patients deep.
Parkland initiated a rapid admission process where they have an internist in the ED, who immediately assumes care for the patient once the admit order is given by the ED physician. Prior to that, you had to wait for the floor orders to be completed by the hospitalist, then wait for nurse to nurse, then transfer the patient. Basically, once the ED physician pulls the trigger on admission, the patient goes into the "transitional" period where they are the responsibility of the floor they have been admitted to, and on the internal medicine service while they make their way up there. Facilities have also created transfer RNs who basically relieve the ED staff of patient care duties once the admit order is placed, and the boarding time has been reduced by up to 25% in some cases.
Just some food for thought. For me, one of the most frustrating situations in healthcare (EM anyway) is when you can't move patients out, and you can't move patients in. You are in healthcare purgatory.