I've actually got some 170* degree lens' on my analog cameras that I've modded and it's not enough. The layout, with my building, home and other areas can't be covered because the way it's laid out. I may not end up with 16 total, but I'm wanting an NVR that can do atleast 16 so if I want to add more, I can without future expenses, besides buying the cameras. I currently have a PTZ mounted about 35 feet up, I'm not paranoid. Once you have a problem cameras are great to have, plus if you find something on your property out of place, you can review your cameras and find out exactly what happened. I've had cameras at each location I've lived in since 1995, it has evolved so much since then, it's crazy. I know I don't have to tell you all how valuable cameras are, especially if you have jackass neighbors.
I took a wide angle cell phone lens, attached it to a few of my analog cameras. It seems rigged, but works great lol. I couldn't find such a wide angle lens to actually replace the stock 3mm lens.
If you aren't familiar with the cell phone wide angle lens, it has a metal ring that has adhesive on it, and the lens itself is magnetic, so it attaches to the metal ring. So just take the metal ring with adhesive, attach it center on your camera's outer lens, and it gives you a super wide angle view. It is a fish eye look, but serves my purpose. Granted your cameras lens has to be a certain mm and needs to be very close to the glass lens or it won't be centered to see through the wide angle fish eye lens.
If curious, I can take a snapshot tomorrow. It was a wild idea I came up with to solve my problem, and it doesn't look bad attached to the camera. haha.
http://www.ebay.com/itm/NEW-Neewer-Detachable-0-67X-Wide-Angle-Lens-for-Cellphone-/271873380798?hash=item3f4cea91be