Just a note about those silly Cisco switches:
Servers have holes in the front and acbk to facilitate cooling. They can do this because the boards can be oriented in a way to facilitate this.
Cisco Rack enclosures have high-density blades in the front(no roon to breathe) and a sizeable backbone in the back (A wall of PCB).
Due to the hotplug nature of the blades, the backbone has to be mounted at the back (instead of using riser boards like in computers). The only other way to have it at the side is by making the server open at the side, like HP9000 computers. This means that every HP9000 rack has to stand alone to facilitate removal of the side panels (the servers are too heavy to slide out). You do not WANT be able to slide a Cisco 6500 out, because it usually has hundreds of cables attached.
The blades, being solid in form, do not facilitate vertical cooling, either.
This design leaves only one possible directioon of airflow: horizontal.
And, yes, it has cost a friend of mine a core-switch when the cooling gave out (there were 3 of them stacked side-by-side).