Can a guy wear a necktie to the office for years and then one day just show up in a bow tie? That would be a long day of answering the same question. How would you begin to explain it? How do you explain it to your wife?? You might as well tell her that you're changing your name. Or your religion. No, I think you're either born a bow tie person, or not.
I must admit that I make snap judgments about the guys that I see wearing them; They fall into one of two groups -- comedians or pompous assholes. In my experience* these judgments have been correct nearly 100% of the time -- and I don't know any comedians.
You should never trust anybody who wears a bow tie. Cravat's supposed to point down to accentuate the genitals. Why'd you wanna trust somebody whose tie points out to accentuate his ears?
- David Mamet, State and Main
By the way, I might as well plug this great website which has the answer to every clothing/etiquette question you'll ever have.
* Lark excluded