I once got 4 flats in one day. The third one was 17 miles from home. Not really a problem since I had both spares and a patch kit and I use a pump.

It's not terribly unusual for me to get two in one day. Like, it happens once every couple of years. probably it's because I'm riding 23s and I'm currently using cheap tires. I'm going for better tires next time I run out.