A note to men...and some women too

First, I would like to say that I in no way want to discourage polite behavior. I really do appreciate the sentiment that is involved here, but there's just got to be another way. I am 28 years old. I'm not ready for "ma'am."

Yesterday I was in line at Cost Plus World Market, and there were two high school or maybe college guys being obnoxious all over the store. They ended up behind me in line. When another checkout opened, one of them said to me, "Ma'am? You were here first, why don't you go?" Pleasant surprise? Yes. And yet, I hardly heard what he suggested because I was so hung up on the "ma'am" part.

What happened to "miss?" When did I stop being "miss?" Couldn't I still be? I mean, when in doubt, I would think you should go with "miss." Or, I am also in favor of going back to using "madam." I'd prefer that over "ma'am." I really am very grateful for the respectful tone, which is all too lacking in our society in general. But "ma'am?" Since when?

Is this because I'm almost 30?