I've had issues with my Bank of Montreal Mastercard at least five times over the last three years. For a couple of those times, my number was stolen and someone tried to buy stuff. Okay, that happens. For the other times, though, there's been a "security breach" and "for your safety, we're sending you another card." That's super annoying because of all the various automatic payments I've got set up with the old, now-useless card number.
But wait, it gets better. I got a call from them just before Christmas, once again with the "security breach" "new card" stuff. I waited for the new card to arrive, and it never did. I called the bank, and they said "Well, it's only been two weeks. Give it another week." I did - in fact, it's been more like a month. No new card. (Fortunately, I watch my statement like a hawk, and I haven't seen any unauthorized transactions.) All I can think is that someone stole the new card, but without the ability to authorize it from my home phone, they've got a piece of plastic that's good for a bookmark and nothing else.