Thumbing around the forums you can see a number of different threads; and why all have different topics they all have the same answer. A in game player rep system.
What do I mean? Just like the forum rep you can add to or remove rep from a user. But I have some guide lines.
1, Rep is account based. This way someone can’t just jump to another character and have a clean slate if his/her rep falls low.
2, Rep modifiers falls off after 30 days. Any rep gained or lost at 31 days or older is removed.
3, You can only mod rep for some one in your party and only once a quest. When rep is changed a message shows on screen letting you know that is has been changed and the value of the new score. Maybe only once in a 24 hour time frame. I am not sure on how often you can add to a users rep… if you quest with the same guy 3 or 4 quests in a row and he is super helpful and what not each quest you might want to give rep to that user during each quest.
4, If no one changes your rep in a 24 hour period that you have played and grouped you get a free bonus amount of positive rep.
5, Your rep total can been seen by you, and group leaders only. Group leaders only see your rep total when your applying to a group.
6, When you give neg rep you also take a point of neg rep. So you better mean it.
I don’t know if this would really help but it would allow me to clear a lot of room on my “friends” list. And would maybe get me to (lead) group more by help me filter out some of the undesirables. Your reputation would be right there for others to see good or bad.
Samius Gurobo 
That system would get abused beyond belief, just like the forum rep system.
So unless you can find away for this system to be honest and actually say whether or not a player is good or bad, rather than be about griefing, then No.
Also different people have very different ideas about who is a good and who is a bad player
That is my point, If i think you did a bad job. Bad enough that I am willing to take a hit to neg you. And when you hit the next lfm (in 30 days) the leader can see your score and use that when he decides to let you in or not.
Now if you get under my skin I add you to my friends list with a note and try to avoid you in the future. But do you know that I added you? Or even that you did something in the quest to get under my skin? Unless you really got to me, were I recall and leave, no you wouldn’t.
Every griefer I’ve experienced in game has the same problem: They’re the ones not pulling their weight. Just play the game, and make your own list if you feel that bad. I do, it has exactly ONE name on it, no one else has been so bad I’ll not throw down with.
I have had lots of people I have added to my do not group with lists. Some for piking, some for smack talking the WHOLE quest/raid some for crying over loot, for for as you said letting the group down. So I do make my own list. I don’t factor in if they are having a bad day-weekend, or if they are new. If they are bad enough to make the list they are done. At least I try to make a note as to why they where added. And can avoid or choose to play with them per my mood.
I feel that i would let my ban list go, if i had a place to see what a person’s rep was before grouping with them. And if they would have made the list before would I hurt my own standing to prevent someone else with a like mind from having to put up with some one.
Maybe less of a rep system and more of a 5 star system…. Do you look at item reviews?
I’ve got my own do not party list and that is sufficient. It even has entire guilds on it as birds of the feather yadda yadda. I can see this only being abused either people having their friends neg someone they don’t like or propping up those who’ve been given negative credit.
Your name is all the reputation you need.