I am going to be teaching a course on spatial programming next semester and was dawdling around the internet looking for books on the topic. I found a book by Esri Press that looked very promising and decided to see if there was some sort of educational discount on it.
There was. In fact, they would send me the book for free if I told them the course number that I was evaluating it for.
I went to type in the details on the web form and found a statement that free samples were "limited to three books once every 4 months." What would you do in that situation? Me? I went through the catalog and found two more books that would be kinda useful. One was a prerequisite for my course and the other would be advanced topics for it.
This is, of course, the same reason why putting up a speed limit sign can be counterproductive. Instead of taking it as a maximum speed, many drivers will treat it as a suggestion of what speed they ought to be
driving. Esri, I am sure, will be giving away far fewer books if they took out that limit on the number of books (or at least informed piggies of the limit only if they tried to order more than three).