Wow, I never thought that this post would result in 5 pages!! I hope that everyone realizes that this did not involve a reservation. This was what is called a "Walk Up." The camper that I was referring to went to the office, paid for the site and left. The park in question was St. Vrain State Park. It is actually very well-run. The staff do a great job. The post was not meant to be a criticism of the park. We actually had a nice stay there and didn't feel too badly about the other site.
As for the general issue at hand, I believe that if I don't want to be at a campsite, I shouldn't prevent someone else from staying there. To me that is common courtesy and to do otherwise would be greedy and selfish. That is the way that I live MY life with the values that I have. I believe that others should do the same, while at the same time fully realizing that many others don't agree.