Are you agnostic about ghosts? Are you agnostic about talking to the dead? Are you agnostic about UFOs? It seems to me the answers to those questions should be yes, yes, and yes. We just can’t know!Why technically? Why the qualification? The essence of agnosticism is that the truth value of certain claims are not known or cannot be proven/disproven -- perhaps inherently unknowable or unprovable.
Again, as the answers should technically be yes, most people do not consider them important enough to acknowledge. In fact, UFO’s exist, we just don’t know what they are. Even if you meant aliens, I would not be agnostic about them either. The universe is only finitely sized, and if the aliens live within it, we can know about them. (emphasis mine)
For example: Life, the universe, and everything came into existence five minutes ago. Everything was created as-is with every person created with memories of an entire life. Each person was created in a specific position performing a specific action.
Should you be agnostic about this claim? Absolutely. The truth value of this claim is unknown and cannot even be assessed.
Usually we apply agnosticism to the realm of the metaphysical, supernatural, and ultimate reality. You can apply it to other things though.
For example: Intelligent life forms exist in some other area of the universe.
We cannot assess the truth value of this claim and it's unknown, at least relative to our known segment of reality. We should be agnostic about it. And, being agnostic about it, we shouldn't care much about taking a position or arguing beliefs on it. Sure, you can try justifying belief in it with statistics or try justifying belief against it using the stroke of luck involved for Earth and life here. Ultimately, it's pointless.
Now, once people start making specific claims about it and about how it intersects with our known reality, then we can start making assessments of it and arguments are justified. For example, we can move beyond simple alienism and into abductionism. One is perfectly justified in responding and assessing these claims. Why always abduct the stupid people? What's with the homosexuality? Why travel all this way just to study us? If you aren't afraid of exposing yourself to some humans, why not all humans? Why haven't we detected you? And so on.
The same applies to the god question. Claim: a god exists. And? There's no possible way of assessing the truth value of this claim and it's unknown and, perhaps, unknowable. There's definitely no way to prove or disprove it. So, yes, we should be agnostic about it. There's no point in even taking a position on it as you can't justify it.
Now, once claims start flying about how this god intersects with our reality, starts interfering and intervening, then we can start assessing that particular claim. For example, Christianity. You can assess the Bible, the history of it, the consistency of it, the ludicrousy of it, the logical contradictions, etc. Belief for or against this can be justified given how much it interacts with us.
Something I see often, including in The Atheist Blogger's post on it, was assessing agnosticism and atheism in relation to "God." Atheism and agnosticism apply to gods in general, not just the monotheistical creator-god. I think we do our discourse a disservice when perpetuating such privilege to the monotheistical religions by extending it here. Furthermore, it compounds confusion for those trying to grapple with application of agnosticism to claims. Existence of a god merits agnosticism. Existence of a specifically defined god may not.
Related: Godly Aliens