Lets see, I have my "good" Nikon that does everything well but doesn't have a built in flash so I also have my plastic Nikon with a built in flash, and there is the older low end Nikon that tends to hunt in auto focus, there is the all manual Nikon, and the Nikon that meters automatically but is manual focus, I need them all. Then when i want to go swimming I need a Nikonos that will not share lenses with the other cameras. Sometimes I need to take a quick shot and e-mail it, or I want to learn how to do something without using up a lot of film so I need a digital Nikon as well. I like 3D photos so I need two Kodak Stereo cameras to shoot that with. I like to hike so i need two Kodak folding cameras that fit in my pocket. For those days when I want detail I need a medium format SLR. I also need a few pocket point and shoot digitals for just in case.
Now I know I could probably get by with a lot less gear, but I do shoot every single film camera I own at least once a month some more than that, if I don't shoot a camera within six months it goes to a new home, that simple. There is only one camera that I allow to skirt the rules a little, and that is the Nikonos it works quite well on land but I prefer to use it in the water so it gets a pass in the winter because the water here gets to be too hard to swim in.
One other thing, my tells me that if I get many more cameras I'm going to need a place to live with them so I don't think I need many more cameras.