Many of us started with the put a camera on each corner of the house and fell into a false sense of security.
I started with the four 2.8mm camera box kit system and I was like "I can place one on each corner of the house and see my whole property and the whole neighborhood." A newbie loves the wide angle "I can see the whole neighborhood" of the 2.8mm fixed wide angle lens. I LOVED IT WHEN I PUT IT UP. I could see everything that would be blocked looking out the windows.
It is easy to get lured in to thinking the wide angle "see the whole neighborhood" because you are watching it and you see a neighbor go by and you are like "Look at that I can tell that is Heather out walking." and "Yeah I can tell our neighbor 4 down just passed by". Or you watch back the video of you walking around and are like "yeah I can tell that is me".
Little do we realize how much WE can identify a known person just by hair style, clothing, walking pace, gait, etc.
Then one day the door checker comes by. Total stranger. Totally useless video other than what time the door checking happened.
Then you realize that this wide-angle see the whole neighborhood comes at a cost and that cost is not being able to IDENTIFY who did it. These 2.8mm wide angle cameras are great overview cameras or to IDENTIFY someone within 10 feet of the camera. At 40 feet out you need a different camera.
And you find that you need more than 4 cameras if you want to do anything more than see what is going on. If you want the video to be useful in a police situation, you will need more.
See this thread for the commonly recommended cameras (along with Amazon links) based on distance to IDENTIFY that represent the overall best value in terms of price and performance day and night.
The Importance of Focal Length over MP in camera selection