After years of travelling to the USA and always locking my suitcase, I invested in a new one so decided to use the black pastic ties instead of a padlock or TSA recommended lock.
I have just returned from Arizona (my second trip with my new suitcase) and on collecting my case in Manchester (UK) there was a new plastic tie on it. On opening there was a notice from TSA stating that they had randomly picked my case for searching. They had then put a new tie on it to secure it.
I am so glad I used these ties as had I locked it my case would have been forced open and ruined.