Canadian Rockies - the best way if you go at high season, is to book in advance with B&Bs - most B&Bs allow cancellation, and they only need your CC number, but not charge it unless you are a no show.
I always ask precisely what their cancellation policies are, and how does it work - have been using B&Bs thruout Canada that way, from Rockies to Maritime Provences, have not encountered any major problem.