The smallest one I have ever felt was 1.9. I know this as I was in the treatment room at work treating a dog, and I suddenly felt dizzy. I then looked at the clock to see how much past lunch it was. In the evening, I checked the PNW Seismec site as was my normal thing to do in the evening why I got home (we had the Spring Break Quake recently before that, so I was keeping tabs), and it was 14 miles from me at the same time I looked at the clock. I think if I had not been standing still on concrete, I might not have noticed it, but standing still, it must have done something to my equilibrium. So I think more people actually do feel the little ones, but attribute it to something else sometimes.
Cedar