Here is a question I recently saw posted on Backpacker.com that struck a cord with me because I also recently took friends hiking up their first 14er and they asked me the same question:
I am new to backpacking and have only made a few serious trips. Everyone I hike with always carries a gun. Do you carry a firearm when in the United States? Or am I just paranoid? Submitted by: Damian – Alamogordo, NM [Backpacker.com]
You can read the response to the question at the link, but in my opinion in most cases guns are not necessary when hiking. When I recently started taking my friend and his wife hiking they were worried about wildlife and criminals while in isolated areas. As I told them wildlife in Colorado is not going to bother you. Bear and mountain lion attacks are very rare. In fact I think the odds of an accidental discharge are far greater than getting attacked by one of these animals. Additionally why pack the weight of a gun you are likely never going to use? Now if we were hiking in remote back country of Alaska or Montana where the grizzly bear threat is very real, then yes I would carry a gun.
As far as needing a gun to defend oneself from criminals I find this to be about as likely as an animal attack. For the most part criminals do not go hiking. From my experience hiking in many countries, for the most part you meet very cool people who share a similar interest in the outdoors as you do. Now if you are walking in a park that borders a neighborhood with high crime and there has been known criminal incidents in the park than maybe a gun is advisable, but I think it would be best just not to walk in that park in the first place.