Fran and I both (and everyone around us) had to show a photo ID, (we used our driver's licenses) at a kiosk to two folks in uniforms, prior to getting to the ship itself. This occurred in I think it was '07 and it was either at St. Maarten or St. Thomas. I think it was St. Maarten but I can't be sure.
In fact we were even advised over the ship's PA prior to debarking to carry a photo ID ashore with us. Maybe there was a "one time" underlying reason, they never explained and we didn't ask. That's the only time we were ever asked.
NCL Epic 2012, Eastern Caribbean
Explorer of the Seas 2009, Eastern Caribbean
Explorer of the Seas 2007, Eastern Caribbean
Explorer of the Seas 2006, Eastern Caribbean