What was Fortunato's crime?

As Poe's "The Cask of Amantillado" begins, Montressor
says:

THE
THOUSAND INJURIES of Fortunato I had borne as I best could, but when he ventured upon
insult.

During the story,
however, Montressor neither divulges any of the injuries nor the insult.  Since
Montressor is Italian and has a coat of arms whose symbol and motto are symbolic of
revenge, the reader must assume that Montressor comes from an honor culture which prides
itself on revenge in response to any individual or familial insults.  The crime could
have been something as trivial as a breech of manners; regardless, it is so negligible
that Fortunato never suspects any offense, even when he finally realizes his
doom.

Just as Iago never gives a good enough reason to take
revenge on Othello, so too does Montressor never divulge his motivation.  In this way,
he is a vice character who prides himself on duping and taking advantage against his
supposed enemies purely out of spite.  It's a kind of
game.

The reader must admit that Fortunato's crime during
the story is drunkenness and gullibility.  He arrives at Montressor's catacombs
inebriated and with a bad cough.  To venture far into the vaults, given the nitre, is
foolish.  In this way, he puts his health in jeopardy.

His
main crime is materialism: he must have the amontillado.  It is a rare possession that
he, a connoisseur, must have, at all costs.  To put his life in danger for the sake of a
vintage wine violates the cardinal sins of pride and envy.