So if there are 4 players and something bad happens to the lead character then one of there lead characters is in for it?
To clear up what I was saying by using an example:
Behind my screen, I have a list of all the characters in order of descending luck score that looks something like this
Ganton Brandon 18
Tutothmus Richard 14
And so on down the list of all the characters still in the party.
Then, each player sets their character sheets in front of them in a column - the one nearest the center of the table is in the front rank, the next in the mid rank, and the last (nearest sheet to the player) in the rear rank.
When something happens, such as a trap being triggered by whoever is in the lead stepping on a pressure plate, I determine who is standing on that pressure plate by doing the following:
1. Ask which character from each player is in the appropriate rank (in this case, the front rank).
2. Find each mentioned character on the "luck list"
3. Tell the player of whichever character mentioned is lower on that list that the character has stepped on a pressure plate and resolve whatever effects that action will have.
Similarly, if there was an ambush from the rear of the party and a lizard-man through a spear at someone, I'd find out who in the rear rank had the lowest luck score and roll the attack against that character.
Edit: the only case in which I do not use the above procedure is when someone says "My character takes the lead," or a similar declaration of specific behavior independent of the party - then, it is that character "in trouble" from any relevant dangers regardless of their luck score - it's proving very helpful for the player that wants his hand-me-down Halfling to die so he can roll a different character.