These situations (blind pass leading to potential head-on collision on MUP) are the ones that make me most nervous around here -- it is not that uncommon to have two pace lines pass within a few feet of one another with a closing speed of 40 to 50 mph. The presences of pedestrians and cyclists adds an unpredictable element and some cyclists get irritated if they have to slow down. That said, I've not yet heard of a mass pile-up so it's probably not as big of a deal as I think it is.