In the U.S. Navy, the line-crossing initiation is voluntary, or at least it was when I was in, but it's kind of expected. One of my roommates aboard the USS Enterprise (the aircraft carrier) was an older warrant officer; he'd become a trusty shellback as an enlisted man, but when he got his warrant, the record was misplaced. So when we crossed the line, he went through the initiation again, with the rest of us slimy pollywogs, so that it'd be in his records again. He was a good sport about it.
In the USN now, it's completely voluntary and there are very strict rules on what can occur during the ceremony. And probably close to 100% of the senior officers in the Navy are (at least privately) completely supportive of the new policy; the old initiation rituals were definitely illegal and were a constant source of concern for Navy leadership.
In a crew of hundreds, there will always be a handful of honest-to-god sadists who would delight in the chance to pour hot sauce on wogs' genitals and make them crawl on hot non-skidded decks. So one trick the ships do now is to have a all-hands call to announce the ground rules, secretly note the names of everybody who complains about it being too lenient and then make sure that those guys are standing watch during the ceremony.
CVN-65, 1976-79, operating out of Alameda in the SFBA; two WestPac / Indian-Ocean deployments. I was also there at Norfolk for the inactivation ceremony in December 2012. They had tours of the ship; it was interesting to see it after 33 years. A lot had changed; a lot hadn't.
