Around our house we have a policy of not opening the door unless we know who the person is and we are expecting them. If I'm home alone I won't even go check to see who it is. It's not a very friendly policy, however it is a pretty safe one.
In today's "paper" there was a prime example of why I will continue to do this. A man was shot after opening his front door for someone. This happened at 38th St and Baseline.
Reading about things like this just seem to deflate me. Hopefully they find their suspect and convict him of his crime.