people really need to learn how to stretch properly. there are all kinds of stretching methods and they have different reasons for existing. its not a matter of, "dynamic stretching is good, but static stretches are not" or anything of that sort. there are dynamic and static methods to aid you before workouts and there are static and passive methods to help your flexibility and prevent injuries and soreness for afterwards. there are also supplemental stretching methods (ballistic, pnf, isometric) to aid your stength and flexibility when you are not training. there is not one kind of stretch that will do it all for you.
this bugs me alot actually, because i have rarely seen an instructor that correctly advises students on stretching, this can be crucial for older students and people with chronic ailments.