Does anyone know the purpose of the Request ID# that's printed on the labels?  I've been working with one of the live help people trying to figure out why I was sent a particular book.  So far we can't determine why-the sender hasn't responded to the live help person's inquiries.  Could the request id be used to try and figure out what the request was truly for?

That number is only useful to the PaperbackSwap Team. If you sent it in thru Feedback, they would be able to tell you which transaction it belongs to. If you have already been able to determine which transaction it is to have PMed the sender, then that number probably isn't going to be of much help.