Colleagues, literate, educated, adult native speakers making a living with words, regularly come up to me to ask, "Should this be who or whom in this sentence?" They're not barbarous. They're not the sort of people who would say, "Her and I went to the movies." They just don't hear it. They don't know whether to use the pronoun as subject or object unless they pause to parse the sentence. And that's in ordinary, journalistic sentences, not rococo Nabokovian constructions.