The polo shirt was first worn by (surprise, surprise) Polo Players in the late 1800s. It was a long sleeved, button down, cotton, collared and probably ugly piece of fabric. The design of the shirt included two functional aspects- buttons down the front of the shirt and a collar on the back of the neck. John Brooks (of Brooks Brothers) began manufacturing these shirts for athletes when he noticed that the sun protecting collar needed to be buttoned up to prevent it from flapping during the player's rides.*
In the 1930's Rene Lacoste (tennis) was the first designer to cut off the sleeves and limit the amount of buttons on his shirts for his fellow tennis players. Polo players also found this more comfortable.
So now we have about 90% of what today's polo shirt is.
I am not against popping the collar if the collar popper understands why he or she is engaging in this fad.
[College Prepster Note: I loved this post!!! My high school crew coach would wear his collared polos "popped" to keep the sun of his neck during hot summer practices. He would always explain that that was the original purpose, not for fashion.]