Why is the front seat of car called shot gun seat?

Qn: Why is sitting in the front seat of car called a shot gun?

I have no clue why it is called so. Anyone has any thoughts on this? Please write in the comments section. I will incorporate in the main blog with your name by the side.
After some research on the web I found very interesting stuff.
Here is the answer from yahoo answers!
"It stems from the days of the stagecoaches when the wrangler would drive the coach and handle the horses and another would sit beside him with a shotgun for protection from robbers, Indians, etc. while the passengers sat behind inside the coach."

The article on wikipedia gives more details on when the first usage of the term was and dwelves into history and where it is first used.

Further reading revealed a game called shotgun. Courtesy http://www.shotgunguide.com/
General Rules
1) The first person to yell "SHOTGUN" gets to ride in the front seat.
2) The remaining back seats may be divvied up in the same manner by being the first to call "back right seat", etc..
3) The word "shotgun" must be loud enough to be heard by at least one witness. If no witness is to be found, or in case of a tie, the driver has the final word. After all, it is most likely his car. (note: if it isn't his car, and the owner is present, the owner's decision is final. Owner must be sober, however, or he will defer his judgment to the driver.)
4) Early calls are strictly prohibited. All occupants of the vehicle (including the driver) must be outside of the building and directly on the way to the vehicle before shotgun may be called. Under no circumstances may a person call shotgun inside a building. For sake of simplicity, a garage is considered to be outside. Parking structures and detached garages are always considered as being outdoors, even if they are underground.
5) A person may only call shotgun for one way of a trip. Shotgun can never be called while inside a vehicle or still technically on the way to the first location. For example, one can not get out of a vehicle and call Shotgun for the return journey.
6) Being as how everyone is created equal, men have the same right as women to the front seat of the car. i.e. women don't own the front seat.
7) One is allowed to ride shotgun as many times as he can call it, but for himself only. No one can call shotgun for their slower friend, unless the friend has a speech or mental handicap that prevents them from calling it for themselves.
8) The driver has final say in all ties and disputes. The driver has the right to suspend or remove all shotgun privileges from one or more persons.

For further rules, please see http://www.shotgunguide.com/