I disagree a bit, I think some people are born with more natural balance (e.g. world class surfers), and to a lesser degree flexibility. But, like anything else, they can be improved with training. Also, balance is specific, so being able to balance on a beam, doesn't equate to balancing on snowboard.
I'm pretty sure balance can be trained just like anything else. Just like anything else, though, there are those with greater natural propensities for it. But I think hard work and consistency trump genetic predisposition any day of the week--call me a romantic if you must. Ross Enamait includes some great ideas on improving your balance in The Underground Guide to Warrior Fitness. You might want to look over his site to see if he's posted any articles on balance training.
I think that a lot of people who seem to have a genetic advantage maybe have just been doing athletics from such a young age that that may be the actual advantage.
True, but I think what EEG was getting at is that even the least genetically gifted of us (in terms of flexibility) can get to a point where we can deliver a kick to the head. That chinese contortionist pretzel shit, that's a different story. More single-limb strength training is a great way to improve balance (in conjuction with drills geared at developing a balance specific to whatever sport you're doing...I've always had exception balance on a basketball court, but when I first stepped into the gym, I couldn't deliver a thai kick spinning on the ball of my foot for shit- you have a base, but it's all sport specific).
