Upon further reflection, Legolas, I think that you're probably right about the undershirt analogy. So it looks like facial hair is the best analogy for a "first anticipated, later dreaded" secondary sex characteristic for men. But I'm surprised few posters here have brainstormed as to why developing girls place such high importance on their breasts that they are either reluctant or eager to get their first bra. I think that the reasoning here is two-fold-- 1) that they don't want to be labeled a slut (as has been mentioned in this thread, actually) and 2) that they are uncomfortable with their unencumbered breasts and feel that they need to wear a bra so their breasts don't feel as naked. But I'm a guy, so I wouldn't really know.