Before my father retired, he was doing research into hypervelocity impacts. It's really intense and pretty scary. He showed me the results of a glass bead the size of a grain of rice that had been shot out of a magnetic rail gun at 17,000 kph (around the orbital velocity of the shuttle, etc.). The glass bead was shot into a steel plate 1 inch thick and ~1 sq foot in size. The entry hole was the size of a quarter, and the exit hole (yes it went all the way through) was the size of a baseball with frozen metal in a splash pattern heading out of the plate.
So, yea, small things can do a LOT of damage at high speeds. That's one reason that sattelites are covered in ~50 layers of mylar. Each layer takes some of the energy out of the micrometerite, so hopefully it will slow down enough before getting to the sattelite itself