He didn't use "xp" instead of points to make it more fun, per se.  He used it to encourage kids to act in a specific manner (get good grades, study, etc) for a specific reward ("xp").

It's called Skinner Conditioning (or Operant Conditioning).

I can see how valuable it would be to a marketing campaign.  Think about it - let's say that for every airplane flight you take, you get a certain number of points.  You can then use those points to "buy" other flights for free, assuming you've obtained enough of them to do so.  Fly with that specific airline enough times, and you could forseeably fly around the world for free.

If that sounds familiar, it's because it's frequent flier miles.  Very good example of the idea.

wigs, people will be motivated to get points just because they receive points.  People do things in Xbox360 games for achievements.  What can you do with those acheivement points?  Nothing, but people earn them anyway.  Same with Acheivements in WOW.  You can't do anything with those points, but people go out of their way to get them.

It is an incentive with no real reward, and people will fall for it.  Not everyone will, but I think it could definitely drive marketing.