ALSO, I think it's even more important to point out that deep stretching with weights will fuck you up if you have too many adhesions. If you have been training for a long time and have not been stretching the entire time, I highly recommend you get tissue manipulation done before you go and do weighted stretches. Muscle fibers will adhere to one another - hamstring muscles glue themselves to IT bands etc. And then if you just stretch the shit out of it, without breaking up that dysfunctional adhesion, you are stressing out and stretching out in the wrong places.
In other words, think of your body like a steak. You want to tenderize the meat before you start stretching the shit out of it. Otherwise you will end up with postural disturbances, nerve damage, and lots of pain without any due benefit.