Ok i didnt want to say this, cause i dont want to look like that guy ... but it so happens that i've hit a few people with bottles before, ok shit happens, I'm not a bad guy i swear.
anyway, when you hit someone with a bottle, the glass shards will disperse with the same amount of force as the original swing, untill acted on by another force. at the point of impact, each individual piece will change direction, and travel outward, until thier momentum is acted on by another force, in this instance gravity.
now if you are talking about follow through with the rest of the bottle that is left, then yeah you could get cut with that. but chances of having small pieces of glass in your dome are slim to none.