I take the point on the security of physical + pin for protection. I guess I'd just love a solution where I could simply switch between accounts without physically swapping something or having a multi-SIM phone.
When I had to travel a lot, I had a small booklet of sim-cards that I could pop into my single-SIM phone (this was the 90s), in most regions I visited to get (much) cheaper rates than I was getting for world-wide roaming from AT&T at the time (this was before AT&T was really Southwestern Bell). Except Japan. (Curse you, and your island-nation cell-phone local-only standards, Japan!)
Heh, I'd disagree. I picked up a dual-sim Windows phone, unlocked, for $150 at the Microsoft store.
I've already taken advantage of it being unlocked by switching carriers (saved some bucks) when I saw the prices on one were now better than what I'd been paying.