There is a saying "good fences build good neighbors" which comes from the fact that everybody wants to be involved with their community but also want a measure of privacy. It is surprising that this saying extends to all aspects of home life except for home security. Many people assume that their neighbors will watch their house when they are not home and immediately call 9-1-1 if things seem off. While this makes sense, in theory, there are many reasons this is an awful way to protect your home.
First, and perhaps most importantly, the only time you can say you have real protection is if you have 24/7 protection. If your neighbors leave while you are out, then you will have no measure of protection. This is not just as night, either, as statistics show that an increasing amount of break-ins occur during the day when people are at work.
There is also the issue that even if the neighbors think something is off, they may never call 9-1-1. This is because of a social psychological phenomenon known as the bystander effect. This means that the greater the number of possible witnesses to a crime, the less likely it is to be reported since people assume someone else will call the police. Home security systems never suffer from the bystander effect and are always prepared to get authorities involved.
A home security system, much like a fence, is a smart investment. Neighbours are good to share a summertime barbecue with, but leave your home security to the professionals.