Scorched earth

[thejeff]

I can see doing it if you were betrayed or were trying to do what damage you could to help a loyal ally. Otherwise... I don't get it.

The only time it happened to me, though I haven't played a lot of MP, was very early in the game. He and I invaded the same indy province, I won. I offered NAP and borders, but got war instead. By the time I'd found it, he'd burned his castle, lab and temple. It still cost me to take it and since I got little out of the early war and took less indies because of it, left me behind and I never really caught up.
The war seemed to be for RP reasons, but I never figured out the preemptive self-destruction.