I used to stretch a lot. Being the obsessive type, I developed a routine that hit all the muscles and took around 15 minutes to complete. I would do this before and after each run, and even on non-running days or after weights sessions.
Something stuck me time and again: most of the injuries I developed appeared to originate from stretching. Not all of them, of course: as any former running shoe user, I can tell stories of runner's knee, Achilles tendonitis and shin splints. But most of them were indeed from stetching.
Over-zealousness was probably a factor. I was not content to just stretch. I had to become really flexible. Overstretching is not good.
I have now stopped stretching more or less entirely.
Why I Stopped Stretching
Other than my tendency to injure myself doing it, I stopped because I read a variety of articles that question whether it is effective. This one suggests it leads to reduced strength. This one suggests it has no impact on reducing running injury.
That said, some studies suggest it may reduce stiffness when done after exercise, so admittedly the evidence is mixed; but for me, mixed evidence did not justify the time I was spending on it - and since stopping has apparently done me no harm, why bother?
Cavemen did not 'Stretch'
Hunters of yesteryear certainly didn't stretch in a way that resembles what runners typically do, so provided we exercise it a way that broadly aligns with what they did, it should not be necessary.
Mark Sisson recommends two Primal 'stretches' - the hang and the squat (at 0:50 in the sprint video). I often do these for a minute when I feel like it, usually after a workout.
Instead of stretching routines, I've started doing mobility work. This is more akin to dynamic/ballistic stretching, which the above study on strength suggests might not have the same adverse effect on performance. Mobility work has the added benefit of ensuring joints are able to go through a full range of movement.
The routine in this video is one I often use.
This is a good website that focuses on mobility.
Chris from Conditioning Research has done a lot of reading around this subject, so to find out more, check out his posts on stretching and mobility.