From a business perspective (I'm not a business major but anyway... ) they may restrict the ability to earn points above or below a moving target as funds allow. For instance, they may restrict everybody from earning over 1400 points because they are near their quota for dishing out Office or XP. On the other hand, they make it very easy to obtain 2500 points for Office if they are running low on keyboards.

You see, I already ordered the Swiss Army Knife (700, no longer offered) and was waiting for enough points to get the carrying case (1500, no longer offered). I should have just loaded up on pens (400, no longer offered) and been done with it.