I've seen popcorn used instead of styrofoam for packing fragile thing nhsbfor ahipping. However the idea of putting a bucket of popcorn on my head to ride a bike doesn't seem that good.

That puts us one step closer to eliminating styrofoam in bicycle helmets. It may be that there are other very good or better materials that are currently too expensive, but whose prices could be brought down by widespread adoption.

I'd be surprised. It's used in motorcycle helmets as well and there's definitely a market for pretty pricey motorcycle helmets if you could claim they were better in any marginal way.