it would be pretty easy to do something like that. You know, purchasing like 50 domains upfront, then handing them out to people who have racked up alot of post points.
If you were to purchase 50 upfront, you could probably get them for like $8.00 - $6.00, then just get a special, private label from a registrar, so people can manage domains right from here.
Or maybe even do a lottery system, where 1 point = 1 entry and then draw one winner each week or something along those lines.
Jim