Security related, but not USA security related:

Going through last week, I realized the pictorial signs at ICN indicate that batteries are not allowed in carry-on luggage. A colleague of mine was asked if he had any, unfortunately told the truth, and lost a bunch of AAs. Fortunately I was not asked, and apparently the x-ray operator ignored my laptop and the 16-pack of AAs in my carry-on. I don't think I would have been willing to give up $350 in laptop/camera batteries, or my AAs for that matter, but what is the deal here?

Anybody know the policy or the reason behind this? Is it just "spare" batteries, or are all batteries really banned in some places?