Thanks new-yawka for expanding my answer!
As far as why Disney would want to buy back points, it may be because to give the buyer more of an incentive to buy because of the break in price, especially if they've just taken a trip to WDW and don't really need those points this year. Also, Disney can turn around and "rent" those points through CRO for cash reservations, so they're not really losing money.
Yes, they only take back the first year's points.