Last night I pre-ordered a D800 from B&H. I then checked my credit card statement on-line to see what happened. To clarify what happens when you pre-order from B&H using a credit card:
B&H puts a "Temporary Authorization" on your card. This is not a charge, but it reduces your available credit limit by the amount of the charge. That is to say, if you have a $5000 credit limit, you order a $3000 camera, and you already have $1000 of charges on your card, you will only have $1000 credit limit left.
This is not a charge: you don't need to pay it, but it could mess up the usefulness of your credit card if you exceed your credit limit. You will only be charged and required to pay at the time they ship.
I am not commenting on if this is a good policy for everyone. It works for me, but maybe not for others. The key is that when they are ready to ship, they will be able to because my card is already authorized and I will not have not exceeded my credit limit. YMMV