My usual run is west up the Boulder Creek path, with a small loop around Eben G. Fine park, and then back. There is a bridge across the creek at the entrance to the park with thick wooden beams as its surface. The wood has seen better days, for sure, but I have run across it dozens of times without incident last year and this year. Yesterday, for the first time ever, it gave me a splinter.
Let me give you an idea of how rarely something like this happens. I walked and ran barefoot all summer last year, from about April to October, and the only wound I ever got was a tiny cut from a tiny piece of glass. That happened when I made the brilliant decision to go for a stroll on the slummiest, frat party-est part of the Hill. Apparently smashing bottles and mirrors is a common pastime in that neighborhood, and after successfully avoiding hazards for a constant fifteen minutes, I finally missed something big enough to cut me. I learned my lesson and never went back to that part of town without shoes, and nothing else managed to draw blood from my feet.
The splinter did not manage to draw blood, but it did lodge itself just deep enough that I needed to stop and remove it with my hand. A pine needle probably could have hurt me worse. I still sent an email to Boulder Parks & Recreation, though. The wood is in visibly bad shape, with lots of other sharp bits just waiting to stab someone. Also, the park is a popular place for swimmers in the summer, and plenty of them walk across the bridge barefoot.
I have heard a lot of people cite incidents like this as reasons for not going fully barefoot and buying overpriced minimalist shoes. For me, the true barefoot experience is worth taking splinters in stride. It does mean I need to be willing to interrupt my exercise routine and check my foot when something happens. To me, this seems the more natural way to do things. Modern exercise seems designed to exist inside an artificial bubble, where nothing unexpected happens, and the only thing that matters is the distance, time, or number of calories burned. I prefer to prioritize the experience.