Of course, you can also team up with those you encounter, but determining whether or not to trust anyone is a difficult prospect in a zombie apocalypse. The in-game chat function usually allows you to get a feel for your would-be teammates, and the psychological games that players engage in is almost as stressful as dealing with the zombie horde itself. Hearing a player yell "Friendly!" as they approach you must always be taken with a grain of salt. Sometimes fellow survivors will offer equipment or consumables like cans of food or soda in order to prove their good intentions, but even this seemingly kind gesture can turn deadly in a matter of seconds.
The scariest thing about DayZ isn't the zombies themselves. It's the fact you're always truly alone and vulnerable.
I learned this the hard way near an abandoned hotel in the Cherno, one of the largest coastal cities on the map. I was hunkered down inside the lobby of the building with an assault rifle and a few basic supplies when I heard sniper shots coming from the tallest building in the city. While I attempted to pinpoint just where the shooter was, an unarmed survivor ran inside yelling at me to take cover. I explained that I knew where the sniper was, but I needed to leave the building in order to grab some food from the nearby market.
In what I thought was an almost suspiciously kind gesture, my new friend offered me his last can of beans and asked if we could team up. I graciously accepted, and asked him to put the beans in my backpack. As he crouched behind me to access my backpack's inventory, I knew instantly I had made a mistake. Then, I heard the click of the spare pistol I had stored in my pack being loaded. I turned around and before I could even plead for my life, I was dead on the ground. It was a momentary lapse in judgment, one that cost me my life and all the goodies I was carrying.
The notion that a player can turn from friend to foe, yet still be playing completely within the rules of the game is something entirely absent from the vast majority of multiplayer experiences. There are no predetermined teams here. The only thing telling you to either kill a player or let them live is your own mind. You can save a player from zombies, drag them to safety, and offer medical attention one second, and then have that same player put an axe into your skull just moments later. Not knowing who to trust is one of the scariest things in life, and that feeling permeates DayZ's unforgiving world
Teaming up with others does offer some very large benefits, however. If you become injured, the best way to regain your health is to scavenge a blood pack from a hospital. Unfortunately, blood packs can only be administered by a fellow player, and if you find yourself in a particularly dire situation - with a broken leg and no ability to even walk, for example - you may find yourself begging a nearby player to fix you up.
The scariest thing about DayZ isn't the zombies themselves - though their guttural moans and coughs are admittedly very creepy. It's the fact that no matter where you are on the map, who you're with, or what weapon you're holding, you're always truly alone and vulnerable. Players can turn on each other in an instant, and they do. You can be taken down by a fellow survivor who simply needed your can of soda, or be abandoned by your teammates after a swarm of zombies has you cornered, simply because they didn't want to waste their precious ammo.
The best part about this unrelenting tension is that the game itself isn't actually creating it - you are. Your mind will play tricks on you. You'll kill innocent players simply because your own negative thoughts have gotten the better of you. You'll fight against your own psyche, and you may reach a point where you wonder why a free game mod has given you more heart-pounding moments than any $60 title ever has.