So... first you register that you're interested, then say, two weeks prior to release, you get an email which says you're guaranteed one if you put down a non-refundable deposit of $200 within say a week (which gives people plenty of time to respond/decide, instead of 24-48 hours). If there aren't enough devices, tell everyone there isn't enough so first respondents get first dibs. If you checked your email at the end of the week, then too bad, even if you're among the first to register, right? That's fair, I would guess, unless someone has a beef about being among first to register and not getting one, but they did have a whole week to respond. In another week, they can make their purchase directly with BlackBerry Mobile since BlackBerry Mobile can't send shipments to partner retailers, because that would break the exclusivity with registrants. But since BlackBerry Mobile doesn't do sales, they send people unique codes so they can buy with their preferred retailer and BlackBerry Mobile would need to shift inventory around depending on where people end up buying. People who choose not to buy in a week, lose their deposit. Oh, but wait, you can give them back their deposit because there's plenty more people that can move up in the list. You refund a few and the next time you do this, the non-refundable deposit is taken advantage of because people know they'll get back their deposit. If you don't give back the deposit, you can always show them the contract they signed and they'll be cool with it?
I guess what I'm getting at is that with limited quantities at launch, there will always be unhappy people that you can't satisfy. You can put mechanisms in place, but that only complicates matters and there will still be unhappy people. The alternative is to produce plenty of devices and risk sitting inventory which hurt you down the line, negating the positive profits at launch.