If its just you, it's not divine. It has to be a collective, a distillation, of the follower's beleifs. Just your beleifs by themselves don't cut it
So the power of belief is a democracy now?

Cool, I want to vote out something!
What about a long-dead evil god with only a handful of cultists (or just one) but a huuuuge amount of power? There's not many believers, but the *quality* of the belief is probably very strong (mad cultists usually don't have many moments of doubt...). They certainly aren't much of a collective...
What about a religion that has a very strictly enforced tenent of "no representation of what we worship"? It's not too out of line (we worship it, it's above and beyond our comprehension, putting it in mortal form would be silly and blasphemous)...and it almost mandates that there be no god...merely a force.
And as for that invalidating a possible Cleric's fall from grace -- it doesn't. You can violate anything you believe in, misuse a power that you've gained through simply belief. If you loose that belief...if you have a crisis of faith....it doesn't matter if it's in a being or a power, it can still weaken your hold to the power that faith gives.
it's not safe to assume that they will be using a concept like "godless priests."
Actually, it is a rather safe assumption since the 3e core books certainly allow divine power not tied to a figurehead...quite the opposite, it's not safe for a book to assume that priests require a god (unless it's something like a campaign setting or supplement that declares that all clerics mut have a god).
Maybe it's just that Planescape has tainted me...after all, if you need a god, how do clerics call on power within Sigil (where divine energies are disallowed), or how do the people of the planes gain tangible power from belief in concepts that, while not incompatible with gods, often supercedes any individual being.
But it's a taint I like!