I don't recognize the person I become when playing Rust alone.
By necessity, to survive, you have to become the most untrusting, paranoid fuck possible. It consumes you. Suspicion is paramount. You adopt a shoot-first, ask questions later mentality, and any attempts to do otherwise are met with disaster more often than not.
As an example, over the weekend I was playing, and I found an abandoned two-story player structure tucked inbetween some rocks in a valley. The location was decent, and it only had one entrance, so I decided to set up base there for a bit. I crafted and installed a door (doors can only be opened by those who place them), making the base mine. I then built two additional doorways, one at the base of the stairs and one at the top, to provide additional security against anyone trying to raid me.
Finally, I started my house in the remaining space on the top floor. Campfire, furnace, sleeping bag, storage crates. Everything I would need to start accumulating gear.
One evening after nightfall, I opened my front door and found another player running around naked in the field ahead of me. When he saw my door open, he began heading my way, and I immediately fired an arrow in his direction. It passed inches from his face, and he stopped, yelling that he had just started on the server and didn't have anything. He meant no harm. He asked if I had any food.
I told him to back up, then I stepped out of my house and tossed some grilled chicken down for him, and then ducked back inside my house. He thanked me, I wished him luck, and he was on his way. A short while later he came back, and asked if he could trade me some raw chicken for some grilled chicken. I was happy to help, we exhanged pleasantries, and he left again.
The next time I saw this guy, he was with three other friends, and they were attaching C4 to the door of my house.
I managed to duck upstairs and close my additional doors before they came in guns blazing. I sat there listening to them hack away at each successive door with their hatchets, getting closer to my inner sanctum. I was trapped, there was no way to get out, so in a final act of desperation, I took what lumber I had and crafted wood planks, which I then turned into a wood wall.
I placed the wall between me and them, creating one final little compartment of isolated space in my house, a panic room, if you will. Doors can be chopped down with some 200 hits of a hatchet, but walls require C4. They were going to kill me and take my stuff, but I was going to force them to waste another explosive charge to do so.
Since Rust allows you to claim "ownership" of land in a way, and create a somewhat defendable home, and also encourages you to stick to the server you chose, it creates a sense of community unlike anything DayZ does. Where you choose to live, and who you live near, creates an entirely unique gameplay experience and entirely new set of choices each time.
Unfortunately, I now open my door for no one. Instinct tells me to be helpful to my fellow players, experience tells me put a bullet in their head and keep walking. If I see other players out gathering or huting, I give them a wide berth. At night, I'm holed up in my little fort, shotgun trained on the door, listening for raiders. I try not to kill naked players... there's no gain, and getting started can be hard enough. So I'll let them pass. I'll chat briefly with some of them... some of them seem really nice. They ask if I'd like to team up and play together.
Sure. Sure I do. But I will not, because I cannot trust you. Maybe we could be friends... right up until the moment I turn around, and you bash me in the head with a rock so you can steal my stuff.