I think one of the main factors in hunting with someone who you don't know would be alcohol. Probably it would be ideal to just have a no alcohol policy but this doesn't always work especially on hunts that may last a week or more and that is someone's vacation as well.
I actually had 2 experiences with this. The first one was on a forum geared towards local hunting, an outfitter made an amazing offer for a week long bear hunt, that's like a few hours drive away from where I live, but it was a group package for 5 hunters. I only had 2 friends interested in going so I asked if there was anyone on the forum interested. A guy replied and said he and friend where interested and that they needed people to. So we exchanged a few pms and I asked him alcohol and if they planned on bringing any if we could lay some ground rules. The guy replies in a huge pm that was basically a huge rant, about his rights, he has a right to drink, he likes drinking, I can't question his right to do so blablabla. Needless to say that told me quite a lot about him and I did not go through with the plan.
The other time I went deep sea fishing in Cuba while on vacation there. The boat held 4 people and I only had one of my buddies interested in going. So two other strangers came as well. They both seemed fine until one of the guys, while we were on the boat and out at seas, started drinking and shortly thereafter he became a complete idiot- yelling and trying to pick fights with everybody else. As you can imagine it pretty much spoiled the entire trip.
When it comes to hunting the danger is a lot greater because there are weapons involved- not just firearms which obviously pose the biggest risk but also knives etc... Now when these idiots have their weapons with them they also end up growing balls of steel and become even more aggressive. These are situations that can definitely spiral out of control.
