Quote Originally Posted by Siosilvar View Post
They do. Double, in fact.
You'd think so but no they do not. The relevant text is in the armor proficiency feats.

from the SRD
Armor Proficiency (Light) [General] Benefit: When you wear a type of armor with which you are proficient, the armor check penalty for that armor applies only to Balance, Climb, Escape Artist, Hide, Jump, Move Silently, Sleight of Hand, and Tumble checks. Normal: A character who is wearing armor with which she is not proficient applies its armor check penalty to attack rolls and to all skill checks that involve moving, including Ride.Special: All characters except wizards, sorcerers, and monks automatically have Armor Proficiency (light) as a bonus feat. They need not select it.
Medium and Heavy armor proficiency feats sre the same but apply to different classes.
Whats more specific, a feat, the armor rules, or type descriptions because this also means all creatures are proficient with light armor because all creatures are characters even if only NPCs. This also goes for simple weapon proficiency.