Q. Why was the little drop of ink crying?
A. His daddy was in the pen and he didn't know how long the sentence was....
I write under several different names, including my own.
One reason is to differentiate the genres you're working in. If you write manly action and sweet romance, you might pick a Manly Action name for one, and a Sweet Romance name for the other, just so your fans won't get confused when they pick up a book by their favorite author and discover that it's far different from what they expected.
If you're prolific, you might write under various names to avoid competing with yourself.
I do share a name with some other writers. That's one reason I use my middle initial -- to differentiate me from them.
When you're picking a name, don't pick anything that's difficult to spell or embarassing to say. Anything else is pretty much okay.