I was doing an interval
I was doing an interval session (5x400m) with my running group on a long, paved bike path a couple weeks ago and took off and carried my shoes (I sometimes wear my Inov-8s with the group because I never know where they're going to run and don't want to get hung up somewhere where I can't keep up BF or even MF). It was the first heavy BF speedwork I'd done and I gotta say, it felt GREAT. I'm certain that my speed was on a par with what I was doing last year when I did Pfitzinger's 55/70 mpw marathon program (Pfitz likes speedwork!), and mainly because of the naked feet, couldn't be from anything else.
My friends got a kick out of it, for sure, except that I was stronger than all of them. And holding my shoes in my hands, which sucks.
But I agree that if you want to get hurt, sprinting is probably a good way to go about it. Pick-up striders, like Danjo described, are a LOT safer and, imo, better training overall for distance runners. Regardless of how you do your speedwork, you should be finishing each rep faster than you started. If you fade at the end, you started too fast (imo) and should adjust accordingly the next time. Think of it as practice for a strong finish.