By Casey Lartigue, Jr.  There is probably an unwritten rule that a celebrity offering to do volunteer work for a good cause should immediately be embraced. Well, that’s not what happened to Jeong So-dam, the glamorous Korean cable TV announcer when our paths crossed on Nov. 29.    Ms. Jeong was the MC of an event about American political philosophy hosted by the Association for Economic Evolution. During my speech about American libertarianism since 1940, I discussed my volunteer work for North Korean refugees. After the speech, Jeong approached me, asking how she could help.  I gave her the same tough love I give to potential volunteers by asking: “Who are you?” After all, if you are Bill Gates, then open your wallet. If you speak four languages, then help with translation work.   So I first stress to potential volunteers: Use your brain. Tell us about your skills and interests so together we can figure out your initial role.  Jeong was good-natured about it, rather than c...