As devil's advocate, there are dog owners that have their animal specifically for security or protection and treatment of them as a family member is a far secondary consideration.

My lab can go in/out on its own and has a inside bed. He is well loved but spends little time laying on the floor in the family room. Of course dog breeds vary greatly but my dog goes barking nuts when someone comes to the door or enters the backyard and he has not 'cleared' them. If the person is not family he sounds quite aggressive. And we like it that way.

No one would get into our house or backyard w/o him knowing and alerting us.

So yes I agree with ireckon that buying a dog for security is misdirected from the point of view of the owner buying the wrong kind of dog for the job, or treating it differently than its purpose, but a dog is a very good investment in long term security.