What I have observed with my chows is this: If I'm not home and they don't feel threatened they could care less about anyone entering our home or getting near it even. In our old apartment there was a bad water leak while I was at work, four strangers came into the apartment, and were working on the leak for hours, even moved their,[the chows'] food and dishes, my two didn't care, they could stay away from the strangers and didnt feel threatened so they were calm and no protective. When I got home, they started guarding me, staying close and staying between me and the strangers, but they didn't growl or become in anyway agressive.
In our new apartment, they bark at everything when I'm home. When I'm not home, my neighbors have told me they are silent. I think chows don't feel the need to guard property so much when owners aren't there, as long as nothing "wrong/bad" is going on. But when you are home, then they are much more likely to become protective. I actually think most well socialized dogs are like this.