Why do rabbits have long ears?

Why do rabbits have long ears?

Rabbits rely on their long ears to warn them of the sounds of approaching danger.

http://www.4to40.com/qa/index.asp?id=749

Unlike humans, rabbits are unable to sweat through their skin. Unlike dogs, rabbits do not pant either. When the weather is hot, they need to lose heat from their body so that they won't die.

Rabbits lose heat by circulating blood through a large vein in their ear. therfore the longer the ear, the longer the path the blood travels, and the more time the blood has to cool down. This is the most efficient way for rabbits to cool off.

http://www.madsci.org/posts/archives/aug97/872210223.Zo.r.html

Elephants flap their ears to cool themselves down.