I've been enjoying Robin Robertson's collection of such embarrassing tales in Mortification: Writers' Stories of Their Public Shame, full of bite-sized vignettes. Some of my favorite authors and poets (like Julian Barnes, Simon Armitage, John Banville, and James Wood) recount episodes of empty lecture halls, amorous (and mentally-unstable) fans, dead pets, mistaken identities, and writerly awkwardness. Judging from these anecdotes, the public reading is the prime site for writer's shame.
The writer's greatest mortification is perhaps summarized in an epigraph from Samuel Johnson:
There is nothing more dreadful to an author than neglect, compared with which, reproach, hatred and opposition are names of happiness.