I'm a decent size guy 5'11 180lbs, i go to the gym and have a Black Belt in Tae Kwon Do, but i still carry my mace of my key ring. I would also suggest that people always pay attention to their surroundings and dont be afraid to ask for an escort to your car, or home. Most taxis here in SF are more than willing to give free rides to people who find themselves in an area where they feel unsafe, or have had another hassle them. Education works just as well, and sometimes even better than selfdefence. Think and be aware. This is America and we are as a nation are very very violent. Once in a while we meet others who wish no one any harm. Be alert. Criminals dont always look like monsters, as our government proves. Nice haircuts, nice clothes, nice cars, well spoken, etc etc are signs of a successful criminal. The nicest people i know wear thriftshop clothing. Go figure.
We also need to keep in mind that humans are part of the animal world. We are predatory in nature and like most other animals we seek the weak ones and those who are the most vulnerable as our vicitms/meals. We are one of the few species on earth that kill for the hell of it. Sad but True.

dai*ma