I understand what you mean. In high school, I was consistently angry because I had the highest GPA in my class, yet the school continually rewarded the "most improved" students with gift certificates to the local mall, etc. I believe the reasoning was that those students needed to be pushed, while students like me obviously didn't need an incentive to be responsible.
On another post, someone mentioned a tax cut for those living a "healthy lifestyle" - within weight range, nonsmoker, etc. If we socialize medicine then this would be a great way to encourage people to lose weight, I think. If the government (state-by-state) decided to pay for pounds (hee I just thought of the program's name!) then maybe it would be a one-shot deal.
However, as things stand, the government shouldn't pay people for any sort of medical issue since medicine is supposed to be privately operated. If Blue Shield wants to pay their customers to lose weight, then hooray for Blue Shield. It may even convince some people to switch insurance carriers, which could be a profit for the companies in the long run (since the companies would now have a bunch of people who are newly committed to being healthy signing up for insurance).