When I first saw this thread, I thought "God no.. My players would never do that.."
And then I started thinking.. A few years ago, when they were being attacked by Goblins.. Our Druid (!) doused her blanket with Oil, and then wrapped it around a dead pine, and lit it up, to cause a distraction, and allow the PCs to escape. They were hoping that it would cause a big enough forest fire that they could escape in the Ensuing chaos.
I was just being a jerk that day

I ruled that the Wargs that the Goblins had with them smelled the oil and fire as soon as it was lit, before it had any time to spread. So that very round, two of the wargs went over to investigate, and found the lone druid, seperated from the party.
Heh.. Poor Iracundia. Somehow, they all made it out alive, but the forest did, in fact, lose a big chunk.