On Pen-Names

Pen-names, pseudonyms, noms de plume.  They are all labels for the same thing; authors publishing a work under a name-not-their-own.  So why do people do it and when is it appropriate?  For three major reasons.

1. To avoid being pigeon-holed: The late James Oliver Rigney, Jr. once picked up a book by an author he liked.  Imagine his surprise when he read it and discovered it was an entirely different genre than he was expecting!  It was at that point he decided to use a different name for each genre he wrote in.  He is probably best known for his fantasy pseudonym, Robert Jordan.  He is far from unique in this however, David Farland/Wolverton is another who uses one name for Fantasy and another for Science-Fiction.
2. For marketing reasons: In some cases when an author's name is incredibly common or hard to remember they change it to something unique and memorable.  Or when their own name would cause an unfortunate double-entendre in their chosen genre (this is most common in romance).  As in the case of myself, some find their name is the same or similar to another, established author.  Of those with my first name, I would say the majority of their last names begin with the same two letters (curse you Scottish surname practices -  just kidding).  Another common occurrence is that female authors take on a masculine or gender-neutral name to draw in male readers (female readers are generally less biased by gender).  A well-known of this is Joanne Murray (née Rowling) who published the Harry Potter series under the name J.K. Rowling.  While not strictly an actual pseudonym, this is a perfect example of this reason.
3. Privacy: Probably the simplest, and yet the most important, reason.  Some people do not want to be famous or at least be recognized in public, if only by name.  I for one want to keep my writing and online persona separate an distinct from my personal life.

In my opinion these are all justifiable reasons to use a pen-name.  What I wouldn't support is using a pen-name.  What I wouldn't support is using a pen-name because it is "cool" or "mysterious."  Pen-names should be used for non-trivial reasons.  So what do you think?