FFXIV introduced a new system to try and promote good behavior in groups. It is a new currency called Player Commendations. At the end of the run, you can give a give a commendation to whichever other player you want. You can use these commendations to buy various unique items.
I'm sure that you are all thinking of the myriad ways this system could be exploited. However, Square did something brilliant here.
You can only give give a commendation if you queued up for the run in the group finder by yourself!
If you queue up as part of a group, you can receive commendations, but you cannot give them out. So to get a commendation, you have to rely on the goodwill of a perfect stranger, someone who you may never see after the run. As well, you only get the commendations when you leave the instance, and you don't see who gave you the commendation.
I think it is an excellent system considering the balance of power in a group. The solo player has the least power in the group, but since she is the source of commendations, that is incentive to at least try to be nice.
As well, the solo player has no stake in who gets the commendation. She will never see these people again. So she may as well give the commendation to the person who deserves it.
Now, I don't know if it has made a large difference in the quality of groups. My groups are always nice, and mostly competent. I've gotten 12 commendations so far. However a good deal of that comes from the fact that I play a tank, and so am pretty much the default option for commendations. I've tried to make an effort to recognize good dps. Judging by the forums, others are making the same effort.
I think the Player Commendation system in FFXIV is inspired. I hope that Square stays with the notion that solo players are the only source of commendations. In my view, that restriction is what really makes the system work.
 Except for Hard Mode Titan. No one expects success in Hard Mode Titan, so the overall mood is not very happy.