There was another thread here that discussed making 'alterations' to boarding passes in order to avoid SSSS. There were differing opinions (and a quite heated debate) about whether or not it was illegal.

There is nothing illegal about buying a full fare refundable ticket and then returning it when one decides not to use it. The day that becomes illegal is the day I say goodbye to the United States of America, and the freedom for which it stands (or once stood anyway).