The rules for this stuff is in the Book Bazaar where you had first posted - the red sticky at the top of it titled "How to use this forum...".
General Rules in the Book Bazaar:
(5) No swapping books-for-books unless the swap is between two "Boxers" (Boxers = subscribers to Box-O-Books). For example, posting "I will send you this book if you will send me that book" or "I will send any three books from my bookshelf for this one book I want" is not permitted unless both members are Boxers. If you are a Boxer, why not peek into other Boxers' bookshelves from the Box-O-Books area to see if books you want are available? You can save a lot of postage and credits this way!
(6) No trying to jump the Wish List "line" by offering or asking for postable Wish Listed books. Postable Wish Listed books should be posted and swapped "officially". This of course does not apply to posts advertising an alternate ISBN (or non-ISBN version) of a Wish Listed title; it is fine to advertise that you have those posted to your account Bookshelf.
And the swapping book-4-book is in the Help Center:
Can we swap books for books directly with other members on this site?
Yes, but only if you both subscribe to Box-O-Books.
"Creditless" swaps are permitted ONLY between two Boxers.
Using the PBS site to conduct an under-the-table book-for-book swap without using credits would be in direct violation of PBS policy, and would put both members' PBS accounts in jeopardy.
Why is this?
We have worked very hard on this site, and it has cost us (and continues to cost us) a great deal of money. The Box-O-Books service is one of the few sources of income the site has generated to offset our financial losses, and we are still deeply in the red. Without some financial support we will not be able to continue the club. We are trying to keep the site free for our members, and Box-O-Books was one innovation intended to help us do so.
PBS relies greatly on the "honor" system among our members. We are pleased to say that the majority of PBSers are honest and above-board; if that were not so, the club could not continue.
We hope that the rule makes sense to you, and that you understand that we are not being unfair or greedy. It is simply that if enough members did this, we would have to close down the club.
Last Edited on: 10/26/11 11:16 AM ET - Total times edited: 1