Well, the internet is not exactly the safest place. There are all kinds of crazies on the net and I am sure alot of people don't want personal information being spread around the net. That is pretty simple answer to come up with
Piss off some idiot crazy person and they go google your name. They now have your personal profile and personal information to come mess with you etc etc. Though my house is more armed than fort knox it would be a tragic mistake for someone to come mess woth my family.
For any crazies out there: I am a honorably discharged US Army Ranger trained with my weapons so do yourselves a favor and stay away from my very very very fine house !
I personally don't mind putting some personal info up here and there. Even though sometimes I think I should not have done that.