This is a duplicate thread from MNK forum. But I think its important:
I am sure every server's got some gil farmers. The only way to stop the gil farmers is not to outcamp them but instead stop players from buying gils. Everyone in the game should take a strong stand that gil buying is a major offense to the FFXI community. Let everyone around you, especially the new players, know that buying gil will distort the game economy and ultimately ruin everyone's gaming experience. Inform the mass that gil buying will not be tolerated. I wouldn't go as far as alienate or punish any known gil buyers. But if we can reduce any further gil buying simply by verbal discouragement, the gil farmer will soon be out of job.
It's the gil buyers that's fueling the gil farmers. If no one buys the gils, the gil farmers will leave.
I encourage anyone that read this to go tell two another people about the problem of gil buying/selling.
"Lowbies, Just say No to Gil Sellers!!"
"Only you can prevent Gil Buyers!!"