Yeah there is a lot of talk lately about some of your bodies mechanisms to protect itself. For instance If we are getting ready to do a lot of weight on a squat our body recognizes the weight tenses up and that protects it from getting damaged (exceptions noted...TOO MUCH WEIGHT, BAD FORM, ETC...) however if we stretch and get so loose that takes away from that and can set us up for unnecessary injuries.
I guess it totally depends on what you are doing. Like Jonflex said athletes need to be more flexible because of their acceleration, deceleration, lateral movements and all sorts of "unnatural positions" they get in.
I'm a big beleiver in hip stretching just because the majority of us sit on forums LOL or at work for hours on end which is an unnatural position and flexes the hip flexors causing the pelvis to rotate anterior, which deactivates the glutes which can lead to over working hamstrings and lots of strained and stressed hamstrings.
I also really like myofascial release or foam rolling just because it releases tension in muscles caused by imbalances. I don't static stretch near as much as I use to and I feel a lot more explosive, I can dunk easier, squat better and run faster with less tightness. I've also incorporated some glute movements like the weighted glute bridge and weighted hip thrusts that have really activated my glutes and I can honestly feel the difference.
Anyway what the freak did I just type, I hope it makes sense!! lol!!