I hope a month is not too long to bring back a thread, but this is always an important subject. I think it's a bad idea to carry high powered lasers for self defense. I also don't think carrying a firearm is a good idea in most situations. At least in the US, there's just too much liability for the victim. I disagree with the way our legal system works in this regard, but my disagreement won't change anything. In modern times, a person not only needs to concern themselves with defense against shady individuals, but also against an imperfect justice system.
If you own a firearm, I recommend keeping it at home. I also wouldn't carry around high powered lasers, large folding knives, nunchaku, throwing stars, kitanas, 8 foot poles, three-section staffs, or any other weapon that makes you feel like the sheepdog of your neighborhood.
If you carry something for self-defense, I'd go with some sort pepper spray. This is probably the best one out there IMHO:
Kimber America Store > PepperBlaster, live OC unit, black
Also, if you're truly concerned about self-defense while out and about, train in some martial arts. Just because someone else has a gun/knife and you have empty hands doesn't mean you have to be at a disadvantage. Your wits, your surroundings, keeping calm, and learning how not to escalate a situation are more valuable to you than any weapon you could have.
My two cents.