It strikes me that POD People should have a policy for the disposal of review copies. My suggestion is the following:
"Review copies may be retained by the reviewer for their personal use. If they do not choose to retain the book they will delete it (for ebooks) or discard or donate it to a charitable cause (for print copies). Review copies should not be resold.
Ebooks that are not selected by any reviewer within six month will be deleted. If a reviewer requests a print book and is unable to provide a review the book will be passed to a second reviewer able to make a firm commitment to providing a review.
If an author has a special request regarding book disposal they should make this request clear in their submission and we will do our best to accommodate it."