I think I remember reading somewhere that the new iBook G4s have a metal backplate for the keyboard, whereas the G3 iBooks have plastic backplates (I don't know this for sure.) If this were the case, it could explain the static.
I have an iBook G4/800, and one of the first things I bought for it was an iSkin Keyboard Protector. However, I noticed that the iSkin would build up fairly substantial amounts of static electricity, and if I, for some reason, needed to remove it or even accidentally shifted it on the keyboard, I would hear the crackle of static, and occasionally would get the full system freeze that wataru described.
I contacted the company that made the iSkin and they said that they had never heard of this sort of thing before (which would also make sense if the metal backplate is new and unique to the iBook G4s.) Either way. I returned my iSkin, and haven't had too much of problem since. I still get a nervous when there's a shag carpet around, tho...