Alien Swarm uses a unique death system, with which when someone dies, they stay dead for good, you cannot choose that marine for any future missions. I for one like this system, as it prevents the game from turning into Sven-Coop with long respawn times. With the system, people have a reason to be more careful, rather than rushing into things.
Anarki has a strong dislike for this system, thus whenever someone dies on a mission, its open season for anyone before he restarts the map. This becomes a major problem when only two people have the major killing weapons (The auto-aiming chaingun and the flamethrower), and thus earn more skill points to improve their weapons even more. So when it becomes 'open season', those of us that are only there for specific tasts like hacking computers or welding doors get slaughtered because we don't earn much along the lines of skill points, and when we do it usually goes to our specific skill. Such a situation asinine and aggrivating, and I would much rather either just restart the map or continue to the next mission with one of the leftover unchosen marines (assuming the game has less than 8 people).