Yep, and beauty of the system is that anyone who is a sophisticated enough user to do that, would never do it accidentally.

Although, I imagine quite a few users --force a command and, unaware of the afore mentioned facilities, write up a nasty blog post about switching to hg from git because git lost their data :)

Sophisticated users make stupid mistakes all the time. They misread output, get confused about the context in which they're operating, etc. Human beings are not machines. You cannot assume that just because a user is sophisticated, they will not make mistakes that lead to data loss. Even the best drivers still have accidents.