Digging up an old post, but was just reading through the forum. I have a 12 camera security system with the cameras inside and outside my home. I have room on one of the monitors for 4 more cameras as well, but just don't see a need for those.
8 of the camera are connected to a DVR monitor which will record video and audio when motion activated. I can also remotely monitor those cameras over the internet using a small application provided with the DVR. Perfect for keeping an eye on the home while at work or travel. But primarily is used to keep an eye on the kids and house while I'm in the basement office. Each camera also acts as an intercom so I can speak to any room in the house with a camera in it.
I do have several stickers on the house or a few windows stating that video surveillance is in use. It's great having a camera on the front door, driveway and garage so I can see who's driving up or standing on the porch before walking all the way upstairs.
Hopefully I'll never have to use any footage for evidence of a crime or burglary. But it's been great for keeping track of what our teenage boy does when he gets home from school and what time he comes home. Can't get away with having friends over without asking permission first.