If it’s happened to us once, it’s happened to us a hundred times: Either somebody picks up a nail in their back tire on the way to Starbucks, or picks one up along the route. The Ducati Multistrada above picked up two nails at once a couple years ago. Why, just last week we were running a bike on the dyno when we all ducked as a nail shot out of the back tire and ricocheted off the wall. Wondering where they all come from is as useless as contemplating why there is evil. All you can do is be prepared, by carrying a tire plugger kit of some kind; even a cheapy rope plug kit from Walmart (and a few CO2 cartridges in case you need to reinflate) will save you and everyone in your group a lot of time and grief.