Two things kill PCs more than anything else I've seen in any RPG:
A.) Complete and Total lack of teamwork (I also roll unrealistic super-ego into this because trying to do it all yourself is a lack of teamwork).
B.) Working completely against the plan/Being a complete dick.
If your players don't work together and it kills them, they know what to do better next time.
I see problem A come up most often, and as a GM I give a little leeway for it, but I don't really fudge that often.
Problem B usually results in one or more PCs killing each other.
For example:
First session I ran with the last group I actually played with (as opposed to GM for, I usually get stuck GMing), everyone tried to tackle the job on their own. I was the only one actually stepping back and looking at it like a team effort. I made it out alive because I used the rest of the group as distractions (if they didn't want to use teamwork, I'd sure as hell use that to my advantage some how), but only one other person managed to get out of the situation and that was the rigger that stayed in the van. The rest of the group wised up quick as the made new characters. Me and the rigger walked away with 60k a piece (was supposed to be 120k for an eight man job).
Session Two went better in that campaign, but we had one guy (you know that one that always has to play a Vindictive, Combat Monster, Paranoid, Chip on his shoulder troll that treats a panther cannon like a sidearm) that ended up getting left behind. And no, it wasn't an accident. After he managed to kill an entire floor of normal wageslaves, blow our cover repeatedly, and cause most of us physical damage we decided he was better off behind bars than in the shadows where we might have to work with him.
Session three he made another big burly troll that was just as impulsive (same character with different ware) that decided it would be a good idea to suppressive fire the room that our extraction target was tied up in (torture style tied to a chair and unable to move). We had already been told that we got no pay if she was injured three times during the meet, and the player knew exactly how the rules worked. So after she takes a round to the shoulder and begins bleeding out (and of course all the baddies in the room is uninjured because they could hit the floor and dive for cover), he decides to take out a HE grenade. My character didn't even wait to see what happened next. He palmed his pistol and shot the troll in the back of the head. We tossed his body to the Johnson as an apology and managed to negotiate for a quarter of our pay (Johnson let us keep the body so we sold it to a chop shop for a decent bit of change).
You can't force people to play as a team, but if they lose enough characters, it might sink in. Remember, their is a reason most runners die within a year in the biz.
