I view it this way: I practice law. Never in a million years would I try to solicit business from a potential client by addressing him by his first name, because it would mark me as a presumptuous ... who assumes a level of familiarity that does not exist. It's for the individual being addressed to say when that level of familiarity exists. It infuriates me that my firm demanded that we use first names on our biographies on the firm's web site, because in effect the firm is claiming that it is entitled to make the decision for us that people can call us by our first names. It annoyed me so much that I rewrote my bio to use the personal pronouns "he" and "his" instead of my name. If someone I've never met calls me and addresses me by my first name, it's usually a pretty good way for that person to have the phone hung up in their ear.

I recognize the nuisance for TSA types moving tons of people through the lines to seize on a name, but there is no reason for them to do so, last name or first name. "Sir" or "Ma'am" is entirely appropriate and universally recognized. If someone is a frequent traveller and comes to know the people at the checkpoint, then fine, a first-name basis is perfectly OK, as long as it is the traveller who makes that decision.