Just ran across this, and wondered, which is right? I'd never run across it before, so I didn't have any style preference, and a quick look through my current story found I mostly used among, but hardly exclusively.
Went looking, and found there really IS no preference. "Among" is not only the most popular (by almost 10 to 1), it's also the older of the two, by almost 500 years).
Looking further, I discovered that I mostly fell into an older pattern, of using "amongst" with words that begin with a vowel (ex: "among friends" but "amongst ourselves"), but this usage has mostly been abandoned quite some time ago.
Given that, I decided the best bet was to simply pick the most dominant & original usage, and stick to that. So now I'll be watching.
So which does everyone use, "among" or "amongst", and why? If, like me, you aren't consistent, then which patterns do you tend to fall into?
It just shows, when you create your own Style Guides, you're always having to update them whenever you find little buggers like these that defy you 'Style consistency' guidelines.