A Muzi said:...
Now that millions of XMart bikes equipped with disc brakes, sloppy
assembly, inattentive owners and CPSC quick releases have been on the
road a few years, we'd expect more than a couple of anecdotal incidents
if the situation were truly dire.
Tony Raven said:...What we have seen is people crash and find
their wheels detached from the bike. But I have seen that happen in
road bike crashes with rim brakes so separation of the wheel is, of
itself, not proof it was ejected by disc brake forces.