Okay, maybe im misrepresentating agnostics with this 50/50 approach. Personally speaking, the agnostics i have debated with never made a point out of saying that it is more likley that god does not exist. Most of them say that atheists are just as unreasonable as the religious. It seems both sides are given equal weight. I know some agnostics that go to church or babtise their childeren, just incase. That seems a bit silly to me. Agnostics like this are sitting on the fence. I think the agnostics that giv more weight to the none-existance of god have jumped off the fence and become a type of atheist. Whatever they are called I think they are more resonable than the fence sitters.
Cheers
You bring an interesting point, On "Objectivism: the philosophy of Ayn Rand" Peikoff writes
"the agnostic is the man who says: "We can't prove that the claim is true, But we can't prove that it is false, either. So the only proper conclusion is: we don't know; no one knows; perhaps no one can know."
Agnosticism is not simply the pleading of ignorance. It is the enshrinement of ignorance"
and continues,
"The agnostic miscalculates. typically, he believes that the he has avoided taking any controversial position and is thus safe from attack. In fact, he is taking a profoundly irrational position. In struggling to elevate the arbitrary to the position of cognitive respect, he is attempting to equate the arbitrary with the logically supported."
As nick points out, there are shades of agnosticism, T.H. Huxley, the inventor of the term defines it as:
"Agnosticism is not a creed but a method, the essence of which lies in the vigorous application of a single principle. Positively the principle ,may be expressed as, in the matters of the intellect, follow your reason as far as it can carry you without other considerations, And negatively, in matters of the intellect, do not pretend the conclusions are certain that are not demonstrated or demonstrable. It is wrong for a man to say he is certain of the objective truth of a proposition unless he can produce evidence which logically justifies that certainty"
At one end you could be skeptic about God's existence on the other you can claim that the question is insoluble, that we cannot prove or disprove God's existence through empirical evidence or deductive proof.
This second position is the one most people mean when they attack agnosticism when it comes to God. This is what Peikoff refers to and what you mean by "50/50".
The subject is not an easy one. and as pointed out before being a "middle of the roader" is probably not a defendable position. For what I have read Rand probably considered herself an atheist. I used to consider myself an agnostic close to atheist just like nick but as I look more into it I'm leaning more towards atheist.
Take the unicorn for example: If one is agnostic about their existence but for all practical purposes uses their non-existence for all cognitive processes, Is one really agnostic? or just a non-believer?
Also I would like to point out that Rand is not objectivism. Rand discovered the philosophy but any errors by her or her followers are not errors of objectivism. for example I don't agree on her use of "Evil" but this does not mean that objectivism should be discarded. As with any philosophy it will get refined with time as new people contribute to it.