I emailed the GM of the Kenosha WI store and this was his reply:
Thank you for taking the time to ask the question, hopefully I can clear it up for you (=
The process has changed a few times and I apologize for the confusion.
To my understanding this is how it works: initially all iPhone 4s inventory that comes in to Best Buy will be reserved for customers that did pre-orders. If there are phones left over after the initial reserve they will be for anyone interested in purchasing one.
We do keep track of how many pre-orders were sold and in what order, so for example if we get in 10 phones and you were the 4th person to get a pre-order you are guaranteed 1 of those 10 phones.
We will not sell any phones to any customer until all pre-orders have been fulfilled.
Let me know if there is anything else that I can do for you,
Mike Frost, GM