I use the local swap shelves as much as paperback swap, and often remove books from here to swap locally (mostly books with close to 100 copies or more already in the online system).  Well, no less than 3 times I have deleted books then looked at my bookshelf later to see the deleted books back on my list!!  This last time someone requested the non-existant book, and I had to regretfully cancel the order and let her know the book is no longer available.  :(  Now I'm going to check at least 3 times before I will trust that a book is truly deleted!!

Just wanted to warn you!!

I've had the same problem when I do deals - I always make sure to check the number of books on my shelf before and after I delete to make sure it changes.