As a former Marine Corps noncommissioned officer, I'm thoroughly appalled by Staff Sergeant Michelle Manhart, USAF posing in Playboy magazine. (Hat tip to Rob at Say Anything Blog.)
The NCO is a rated link in the chain of command, and is almost always the most important one. The NCO's authority is legally derived from the authority of the chain of command, but that's not the actual source. In reality, an NCO's authority is a product of their subordinates' respect for the NCO's technical knowledge, self-discipline, and overall moral character. Those NCOs entrusted with recruit training (as SSgt Manhart was before the USAF suspended her duty assignment) must be the best of the best in these measures.
Once SSgt Manhart's subordinates have seen her without her clothes on--or, for that matter, even heard that she has posed nude--that respect is going to disappear. The men will look at her as a sex object; the woman will simply view her as a slut. Neither will take her seriously.
It's hard to get respect for your AUTH-OR-I-TAH! when you've willfully flushed it down the toilet.