I have made it a habit to not stretch prior to, or after for that matter, running. I know. I'm headed straight to running purgatory.
I've never had any muscular problems, other than some slight soreness the day after a hard run. That's not a problem since I never run back-to-back days. Ergo, no need to stretch. On top of that, I have done the requisite research into the benefits and threats from stretching...and found very little either way that sways me. I can theoretically see the benefits, but it doesn't work for me, and I just don't see the downside based on my results. So there.
But I do have a caveat: at about mile 10 of the 2007 Houston Marathon I had a severe calf problem that caused me to stop running and find a tree near Rice University to stretch against. It gradually worked and within three miles I had forgotten about the issue. What caused it? I can only guess it was all the stride-shortening and -chopping I had to do in the first 3-4 miles. Since I never run with other folks, this congested running early on was a little disconcerting. Maybe this had no effect on the calf, but maybe it did.
And the other caveat (can you have two and they still be caveats?) was in this year's Houston Marathon. I had severe cramping starting at mile 23 through the finish line. But I don't think stretching had anything to do with it. Full body cramping, from one toe to my neck and almost everything in between, isn't due to a lack of stretching. Dehydration, maybe. Too fast, too far, maybe.
But not stretching.