Now, I know I'll get shot for saying this, but here goes:
As a server admin, I'm completely fine when people burn stuff. However, when they burn it so badly that an entire region is lagging at 1FPS, that's where there's a problem. Moreover, can you imagine if some ass put a TNT block every 2 blocks on the map and then detonated it? I sure had to experience that. The only choice left here was to IP ban these types of griefers.
Azrooh - Hacked up some TNT and flew around putting explosive swastikas all over the place, then blew up a huge chasm around spawn so nobody can get anywhere due to falling damage deaths. Started blaming other people when he was caught and said he'd ban them from Minecraft.