Aside from personal commitments, it's only because of player disinterest do I ever get demoralized enough to call it quits. >.<
Writer's block seems to only hit me when it comes to one-on-one RPs or when I'm playing a single character.
Edit: Okay.
I'm having a hard time coming up with a plot... and i know it might be lame to switch gears so late when people already have character concepts, but what do you think of this?
It's the year 20XX on the planet Earth. Since the end of the Meiji Restoration, the ninjas clans have spread throughout the far corners of the world. There are no shinobi who go by the name of Uchiha, Hyuuga or Uzumaki... There are, however, the clans of Iga, Kōga, Hattori, Katō, and many others are still thriving. Based on the historical ninja clans of feudal japan, these schools have spread all across the world. No longer purely a japanese thing, ninja exist in every continent across the globe in secret. Some of these clans have done nothing more than train young children in their ways, while others have served as international spies or government agents, and many serving only their own ambitions.
The PCs are members of these clans. Perhaps all from one place, or from around the world.
The setting would actually be D20 Modern... with a little bit of futurism thrown in, I think. The geopolitical landscape might be vastly different from modern day Earth, so as to present the maximum amount of fun and conflict.

What does everyone think?
CharGen would otherwise be the same, except plot-relevant things unique to Naruto might be absent (Ie: No tailed beasts, no seven swordsmen or kages, although a form of hidden villages might exist, sharingan wouldn't have any meta-plot relevance like it does in the canon) ...which wouldn't really effect any of the PCs as far as I can tell.
Most of the clans have become fully absorbed into their respective cultures or host nations. A clan in Africa, for instance, might have a japanese name and origin known only to them- but all the members are otherwise indistinguishable from the common populace, some without any japanese blood in them at all- and those that do might be 1/16th or something.
Others might have no relation to japan at all. Perhaps the legends and myths of werewolves were in reality the rumors of a 'ninja clan' in Europe. Ninjas in all but the name.