Walter, reading your response comment, I have no doubt that you could handle your FSBO with some confidence.
Do you really need a listing agent... no, of course not. Full service agency isn't for everyone. Most people don't feel comfortable marketing their homes, dealing with the public, making appointments, pricing their homes, and handling negotiations and the aftermath all the way to closing. But for those that are comfortable with the plethora of typically unfamiliar duties... more power to you.
btw... if you do a little more research, I'm sure you can find a resource that will put you on your local MLS for waaaaaay less than $700.00