Mani the Monkey -- the youtube climbing coach -- notes that many people use inefficient or inappropriate grip techniques throughout their early climbing careers. As a result, he notes that it's incredibly important for beginning climbers to "incorporate the whole spectrum of climbing grips as early as possible in a climbing career." This will allow one to avoid injury and continue to grow in strength.
In review, Mani notes that there is always a "least aggressive way" to take a certain hold, and a "most aggressive way" to take a hold. Taking a hold via the most aggressive way may lead to injury. And the most aggressive type of movement is the full crimp.
The full crimp takes force away from your muscles and puts it into your tendons and joints. Deferring this force away from the muscles and into the joints and tendons can lead to injury. Indeed, Mani says that, "unless you're a competition climber, you should never crimp fully indoors."
The video also reviews several other types of holds and grip types. The take-away is that you should work on all styles in order to be more effective on the rock...
--Jason D. Martin