Who and whom … does the latter term matter to you?
From The Economist:
Since whom is becoming less common, many people can’t use it properly even when they are aiming for Formal. (A common mistake is using it in a subject role, for example: That’s the candidate whom I hope will win the election. Here, the mistake is in thinking that I hope turns who into an object. But the clause is really who will win the election, with I hope just an interpolation.) The unease over whom just makes people avoid it more.
I think whom has a long life left in it, though, for non-grammatical reasons. Educated people prize language, and the mastery of Formal. Their status at the top of the social heap is an incentive to treat the proper use of whom are a sign of intelligence, not just the Formal register. They do most of the edited and published writing we consume. And so whom will live in print for a good long time, even as many of those same people ignore it when they’re chatting at the proverbial water cooler.
Kids will go on reaching secondary school being taught, for the first time, how to use who‘s strange cousin. The will also be learning a meta-linguistic lesson: sometimes you don’t use the language that comes most naturally to you. And finally, when they have kids, they’ll start explaining the whole strange story to them in turn.