I know this post's title is a little sensationalist, but I couldn't help myself.
I believe self defense is often misunderstood by the majority of people I come into contact with. Say the words self defense and the majority of people think of brutal martial arts techniques, weapons, and firearms. In most cases, I believe all three of these are counterproductive to the goal of self defense, which is self preservation. A majority of people I speak to, men and women alike, see self defense as a violent repelling of an offender. While this has its place in self defense, it should be a small part of one's self defense training.
The larger issue, and one that is often overlooked, is the negation of physical violence through verbal posturing, de-escalation techniques, body language, and awareness. I have used each of these facets of self defense in the real world many times (in Iraq, as a social worker in Toledo, as security for an Occupy encampment), but I have never needed to use physical force in order to protect myself.
Martial arts is a percentages game. All the blocks, strikes, and techniques increase the likelihood that you'll win a fight, but there are no guarantees. A high level boxer has a good chance of beating a normal man in a standup fight, but the improbable can happen. Sometimes the improbable is personified as a sneaky bastard with a lead pipe that you didn't see. Sometimes it’s a knife, or a gun. You can execute a perfect double leg, take mount, and start viciously beating your opponent, but none of that matters if his buddy boots you in the head and sends you into a comma. Martial arts, firearms and other weapons can increase your odds of survival in a worst case scenario, but if you stay out of physical altercations all together, your odds of surviving a dangerous situation are much higher.