I've seen client-side certificates work in large organizations (e.g. MIT). However, this was in the pre-smartphone era. They just had to support IE, Safari, and

I've seen client-side certificates work in large organizations (e.g. MIT). However, this was in the pre-smartphone era. They just had to support IE, Safari, and Firefox. That was still a pain. Today, it's much harder to support every browser and OS.