This spring, I've had two flats on two different bikes, about two weeks apart. Each bike was sitting in the garage when the tire went flat. In both cases, there was a single tiny hole on the rim side of the tube. The rim tape was intact in both wheels, and I could find no debris or anything that could have caused the flats.
One was weird enough. But two identical, unexplainable flats? How the heck does that happen?