Designed to fit an ARCA-SWISS Dovetail Plate (Arca-Swiss dovetails are a commonly accepted platform industry-wide for photography and is now seeing some use in the cinematography/videorgraphy industry because of HDSLR cameras), the cable boss is designed to organize your cables and more importantly; protect your camera from damage. Arca-Swiss brackets are common accessories for DSRL cameras. Besides offering additional structural support and protection, they have Arca-Swiss dovetail slots on their bottom and side which allow you to mount the camera into an Arca-Swiss clamp equipped tripod vertically or horizontally - a very handy thing if you are doing product photography.
What makes the cable boss so awesome is that its main function is to protect your investment. There is an inherent weakness - a flaw of cable design in general - regarding the cable connectors inside your camera. Yank an HDMI cable out of your camera at an angle and you risk bending the actual plug inside the camera - which can break the tiny little solder - pin connections - and cost you hundreds of dollars at your local authorized camera dealer in repairs (mainly because they won't repair it they'll sell you a new board for your camera - a very expensive solution). The cable boss is designed to clamp your cables in place making it impossible (or very difficult at best) to damage your camera with an accidental tangling of the cables and an unfortunate yank or wrong move. In all honesty you're now going to be more likely to pull the camera and tripod over... but you should feel the weight shift long before that actually happens (I know because I've seen it happen several times).
If you are going to be attaching an external monitor, microphone, slave speedlight unit, remote shutter release, etc... - anything that you will need to plug into your camera - you shouldn't even question is the $25 for the cable boss is an expense you need to incur. Just think of it as very affordable insurance.
Photography & Cinematography 101 - © Jon Patrick Hyde 2015