Quote Originally Posted by Dark Summoner
Lulu: "The Fayth are people who gave their lives to battle sin."

Basically this means that the Fayth only existed to destroy Sin. They dissapeared after Sin was defeated by Yuna, so it would not be possible to create more fayth. pointless too..
This is said when they had no idea how corrupted Yevon is about and this is what Yevon tell them. If that is the case, then the fayth that dreamed/summoned Dream Zanarkand cannot come about.