Originally posted by wasser You can read all about the reasons
For the K-x, you can also look at p-41 of the K-x manual. For the K200D, p-39.
For the K-30, similar to the K-x, the manual (p-46) says this about alkalines:
"These are easily obtainable when the batteries you are
using run out but they may not support all the camera
functions under certain conditions. Use them in
emergencies or when checking the camera functionality."
Notably, alkalines also die quickly once things get cold, while the other battery types handle cold better.
This is all reflected in my experience of the K-x and K200D, and flashes too. Alkalines suck.