Different camera bodies have different maximum shutter speeds. For example, the base model Nikon D3100 has a maximum shutter speed of 1/4000th of a second, whereas the top-end Nikon D4 has a maximum shutter speed of 1/8000th of a second. Very few people will ever need to shoot above 1/4000th of a second. 1/4000th is sufficient for any sports or wildlife, even hummingbirds. Even if you have the need to go faster, it’s difficult to get enough light to allow your camera to exposure at that shutter speed without using a very high ISO. Therefore, the maximum shutter speed isn’t a factor for most photographers.