No. I have never thought about limiting myself in that way.
Farmers markets are great places to buy some foods. Certain foods are superior in quality if you buy from local sources. Actually most fresh fruits and vegetables don't travel easily. Tomatoes are an excellent example. The ones shipped over the world are too watery to taste good. The local tomatoes have more "meat" and taste great. The best tomatoes come from your back yard. Still, something like bananas would be hard to buy locally.
That's a great idea, I had not heard of the 100 mile diet before. When I was a kid, it was probably more possible than it is today. We live in a rural area and people used to grow almost every thing they ate in their gardens, orchards and even their beef, pork and poultry, it is not the case anymore.
Not sure if it is because more people work outside of the home than before or if the cost and convenience of buying food became more prevalent.