Isn't that the very risk we've all accepted by investing, though? That our target retirement date will be the next 1929 or 2008? That's why many investors become more conservative as they near retirement.
Sometimes I feel like some people have deluded themselves that there is no risk in investing since over the long haul there are consistent returns, but our individual long hauls, however long, have an end date, and depending on our age and ability, we may not be able to extend that date long enough to recover financially from a crash.
I think knowing and accepting that risk is important. I didn't feel discouraged reading about it, but maybe that's just me because I tend towards imagining worst case scenarios. :)