fine them a lot more, say $10 for every user they left vulnerable and make them sign an agreement to protect customers "properly" and "fairly" or face very harsh consequences in future.
a $10 fine for leaving 1 persons data unsecure and vulnerable is extremely low but the total would be immense but well deserved. even a $1 fine per user would see them never repeat their slack actions
considering
@
marty370
is banned temporarily, i have taken the liberty of voting to leave sony alone on his behalf :P