As far as in store pre-orders... if the game slips or drops from radar I'm guessing it's the same as if you pre-order a game and then don't pick it up. The money you put down becomes theirs at some point with no refund. I can't remember the time period but I had it happen to me once years ago. Doubt it was DNF but it may have been.
If you only put five or ten down they will hold the game for two days before they are allowed (by store policy) to sell it to another customer. The guys at my favorite store will hold a game for me until I get a chance to pick it up or until they make contact with me about my intentions.
Not sure about the policy when you've pre-paided in full. Also if you pre-order for in-store pick-up via the Internet but don't pick it up the website says their is a restocking fee. After seeing that I never pre-order via the Internet again. Unless I wanted it shipped to me.