I'm sure that Zane uses Atium beads because:
He has a bunch, we know this, why would he have it all if he didn;t need it
the times he's used atium he was going into the city for a purpose that would require it(attacking Cett, and confronting Vin)
He's not afraid to keep metals in his stomach overnight, and he has lots of atium, why wouldn't he injest it, just in case.
As for Vin earring, I'm pretty sure it's more than a false lead, it has to have something to do with hemalurgy.
And the Atium spikes, what was said about them not being atium, because they didn't use them for funds, makes a lot of sense. Remember, Marsh didn't start acting really funny until book 2, in book 1, he's still mostly himself, and he says the inquisitors didn't know where the atium was, I thihnk he would reveal if all the inquisitors had a huge atium spike in them, at least in book one. I also think Elend and Vin would be very conscerned about learning about the inquisitors, because they woudl be some of the main threats to the throne.
I still the think the are mist born because of the metal ( the one elend ate), and that hemalurgy is something else, that gives them other powers.
CONTINUED FROM MISTS THREAD:
I'm just saying that they might have to be seekers before hand, we know they have all the powers of a mistborn afterward (even though they might come from a different source). I just thought of this, The well beats with pulses, Ruin is in the well, Ruin speaks to hemalurgists, it seems Ruin is related to the pulses that seekers, mistborn, and inquisitors can hear. Many of us thing that Hemalurgy has much to do with Ruin, so what if being a Seeker, and being able to hear the pulses is important in the ritual that makes inquisitors?