The Mount is possibly the most dominate position after taking someone's back (although Eddie Bravo believes the Spider Web is the most dominate position). I don't think of it as a position. It is more like a skill. In MMA or a self defense situation this is a great place to be. On top where you can rain down punches into your opponent's face.
Unlike Side Control or the Guard which are very stable positions that you can hold, the mounted position can be unstable. You can be easily reversed until you have mastered the skills needed to stay on top.
You have to flexible and develop a good sense of timing and balance to be effective.
It can be like riding a bucking bronco in a rodeo show. Especially when you are dropping bombs on their face. When you're on top your opponent will buck, try to roll and may even take a wild swing toward your head.
If you are on top and you are squeezing your knees together which helps to maintain the position but you are not flexible enough to release the tension when your opponent bucks, you could end up on your back playing guard.
Although the Guard can be a very dangerous and offensive position, the reality is that you just took a step backwards. You went from the top position where your body weight is working against your opponent to the bottom where their body weight is now working against you.
Like the Rubber Guard I think of the mounted position as a system of different positions.
Within the system there is the classic low mounted position where your weight is back over your opponent's hips and the high mounted where your knees are squeezing in their armpits with your weight on their chest.
There is also the S-Mount, Yoga, Double Grapevine, Butterfly and the Gangsta Lean. There are also variations of the HM where you can pin down one of your opponent's arms.
