Actually, generally speaking there are three types of stretches: static, ballistic and dynamic. Ballistic stretches propel you fast and hard into and out of the desired range of motion, and yes static stretches are entered into, held and withdrawn out of slowly. Ballistic stretches are largely discredited as a safe and effective means of enhancing range of motion.
Dynamic stretches come somewhere in the middle; they are more slowly performed, but you are in sustained motion and you don't hold the stretch for very long. You see more dynamic stretching protocols in group fitness classes these days, as you also see in Cathe's workout as well.
There is some controversy as to whether or not warm-up stretches do prevent injury; in fact, a recent article in my ACE-Fitness publication addresses that very issue, and stated quite clearly that the research into this area has been, to date, quite poorly designed, thus we can't make any good conclusions. I prefer a brief, dynamic stretch about 5 minutes into the warm-up, and an extended stretch at the end of the workout.
a-Jock