FYI: This is common practice for thugs. They knock on the door or ring the doorbell and if they see/hear nothing, they figure nobody is home so they go around back and break in. So, even if you don't want to answer the door, make sure you at least turn on a light or two when someone "visits" to make sure they know someone is in the house. Just having a motion light is not enough. Those go on even when nobody is home. The thieves want to rob you, not confront you.
A few years ago I happened to get home to my place in San Diego around 2:00 a.m. after a gig. Around 3:30 or so, someone rang my doorbell several times. Thinking it was just some kids playing around, I ignored it. 10 minutes later, I hear hammering at my front door. The idiot sat back and saw that "nobody was home" so he was trying to pry open my door. I turned on the light and yelled to the guy that I had a gun and had already called the cops. He ran for the hills. The cops never caught him. I don't ignore a knock or doorbell anymore.
We recently had a young guy, possibly in his early twenties, come to our door around 9:00pm on a Sunday night. He spoke with a fake accent/stutter and was trying to sell magazines so he could make money to help troubled youth. What made me uneasy was the fact that it was pretty late and he was dressed in all black. I immediately called security and gave them the description that my husband and I took down. I'm pretty sure they were scoping out places to rob and I wouldn't be surprised if the guy who came to our door was one of the men recently arrested. I agree that you should always make it known that you are home if someone like this comes to your door. However, if my husband was not home with me I would have not answered the door but instead I would have called the police.