Increasingly I hear people use this word to mean deeply upset or annoyed. Is this an accepted change of usage, or am I justified in shouting at the radio every time some lad in a band talks about being mortified when he heard about the Croydon Cat Killer? Why, are you the Croydon Cat Killer?
Well, I don't know anything about the Croydon Cat Killer, but might another reason for being mortified on hearing about them that you come from Croydon yourself - so you then feel ashamed that some might think Croydon is the kind of place that fosters cat killing?
But I suspect that you are right and some are using it to mean deeply upset. This kind of blurring happens with word meanings all the time, doesn't it? Pedants' Corner is the place to object to it, but it's not going to stop the trend!