(This is based on a response I posted on Baldr Odin's blog "A New Trajectory")
There are some that believe that some studies (such as the flawed Kellermann study) prove that a firearm in the home is more likely to kill someone in the home than an intruder. The flaw with such studies like Kellermann's is that it tries to suggest causation from correlation, and doesn't take into account enough factors. Such as, how many defensive gun uses occur when no shots are even fired? Or, what about the likelihood of firearms and violence both accompanying illegal activity such as drugs and gang activity? Sure, a firearm present will increase the possibility of someone being shot rather than other weapons being used if someone is intent on harming someone in their household, but you have no proof the firearm is nothing more than the tool used for the crime - not a cause of the assault.
Protecting my family is very important, but it's not the only reason I own firearms. Plinking and clay target shooting are a fun, safe family activity. I use firearms to teach my kids responsibility, safety, and marksmanship.
There are some that believe that their perceived "risk" of having a gun in their home isn't worth those benefits. Consider that I also ride motorcycles (I'm a motorcycle safety instructor, actually). Riding a motorcycle increases the risk of being injured in an accident, yet I manage that risk as best as I can, because the benefits (feeling of freedom, enjoyment of riding with friends and my family, huge gas savings) are worth it to me.
I manage my risks riding motorcycles by wearing proper gear, making myself visible and my intentions known to other drivers, constantly working to practice and improve my mental and physical riding skills, and making sure my motorcycle is well maintained.
I manage my risks with firearms by keeping all my handguns except my regular carry gun securely locked in a lock box (My carry gun is always either on my person or next to my bed when I'm sleeping), my long guns are kept far separate from the ammunition, and my two teenage children are well trained in firearms safety and I trust their responsibility that they're not going to play with the long guns (or try to get into the handgun box) without my permission.
Perhaps riding a motorcycle or having a gun in your home aren't worth the risk that some perceive, and that's their choice - I respect that. My choice is to do both, be well informed on the risks and to manage that risk wisely.