I'm wearing 8 pieces of light Armor (a full Dark Brotherhood set) on a new character letting crabs smack me for Light Armor skill-ups .. and suddenly I see an 'Unarmored Skill Increase'.

Er, why? I double-checked, I have helm, cuirass, greaves, left and right pauldrons and left and right gauntlets, what part did the mob hit me to score a hit on an unarmored body part? hmy:

[edit]

I checked, no piece is down to zero condition.

Shield?

Boots

If you arent using a shield you can still be hit in an 'unarmored' area, thus raising the skill.