I never bother locking my luggage anyway...
On the basis that anyone who wants to get into it would be able to get past the locks in seconds anyhow. The person most likely to be inconvenced is me, too jetlagged to remember combinations or find keys.
I am also honestly surprised that these TSA Master Keys weren't $5 per set commodity items even before this print-your-own thing, because all the lock factories (mostly in china) must have the masterkey specs to make the locks they fit into. Presumably .gov must have leaned on ebay to strip out listings?