Are you providing free Exam and Desk copies of books being considered for course adoption? (firebrandtech.com)
Instructors can also request one complimentary desk copy for every 20 copies of a book ordered. (ohioswallow.com)
Last year, in 2012, they decided they didn't like having their books scavenged by book recyclers buying desk copies... in their mind, if a professor sells books, they don't honestly look at them for adoption. (thefutureofpublishing.com)