Within my writing circles, discussions about pen names have come up frequently of late. I guess it's because many of my writing buddies are turning their attention to self-publishing, and many of them have one reason or another to not want to use their real name.
In fact, if I think about it—I mean really think about it—none of my writing buddies publish under their real names. For one writer, it's because she wants to separate her publishing from her real life (so her students can't find her online). Another wants to protect her children from what could become negative backlash if other parents work out the connection between the two names. For another, it's because she wants to separate her fiction from her nonfiction. And for another, it's because their day job would be at risk if their employer ever worked out the truth about the nature of their fictional writing.
Regardless of the reason, it's always interesting to see how others come to the conclusion about what name they want to publish under.
And for me… I laughed at myself when I discovered that I had made the decision about my pen name back when I was just starting high school.