It's not an exploit. It's simply a repeatable quest. here's the full skinny on fame. you can get rank 9 fame without doing any quests in any city for less than 10k. the trick?
Million Corn
Selbina Quest. there is an old man with two sheep wanting feed. 3 ears of corn. you can buy corn at a NPC vendor. (Look around town or ask) and trade him the corn. you will make most of you money back.
This single quest builds fame in SanDoria, Bastok, Selbina, Rabo, Jueno
Cornette Quest. as explained above.
This single quest builds fame in Windhurst,Kazhaam, Mhara
just buy doing two simple quests you have covered all towns for fame. now that you have rank 9 fame in every town you have access to all quests and avatars. also you can get rank 10 fame. (it doesnt have a fame message.) and with rank 10 fame comes very generous price deductions at stores. and increased revenue of items sold to NPC vendors.
for a good website on how to build fame check out
http://somepage.com/ffxi/fame.html