Yeah, I'm inclined to agree that bringing along a weapon for defensive purposes is pretty well asking for trouble. I have a small Swiss Army knife that I carry always (ie, even in my purse to Church), which I use for exciting things like slicing apples or cutting gauze bandages to fit small scraped knees.
I far prefer to avoid dangerous situations, by applying the best defensive weapon of all - common sense - being aware of my surroundings and not doing stupid things. I'm sure all of you talking about carrying weapons can handle all the alcohol in the world (because you are young, strong and invincible), but since alcohol has been known occasionally hinder one's judgement and reflexes, if you've been out for a rough night and get into a little mix up, your reflexes might not be spot on if you do bring a weapon into the fray...which could lead to rather unpleasant consequences.
Nowadays, I have my children around to protect me (believe me, kids grant extreme immunity in some parts of the world), but back when I traveled on my own, I had the common sense to not get wasted and then wander around on my own. I did walk down back streets between bars and train stations, in port towns where I didn't speak the language, at 2 in the morning...and I'm a GIRL!!! and never had any problems I couldn't resolve by moving fast, looking confident and being aware of the people around me. I just read up about local dangers, and avoided them. Been traveling and living overseas for most of the last 15 years, and I've never been mugged, assaulted or worse during that time. (Where's the touch wood smiley?!
Bottom line, if you go looking for trouble, it will probably find you.