I didn't know to put this in the Scarecrow thread or Sinestro Corps thread, so I put it here. Any mod can move this to where it rightfully belongs.
Anyway, I was thinking about it, and I had a thought. Scarecrow can use his fear gas to cause fear in others. The Sinestro Corps rings are powered by fear in your opponent. Do the math, it's a perfect idea. Has it ever happened?