My son Ben mentioned that he doesn’t know when to use whom - he just guesses. That is largely as it should be, even for an editor’s mind like his. As the generations turn, we see the changes. The number of 25 y/o’s who would even care is small; as his peer group would include an unusual percentage of those who do, it is small wonder he would be aware of the lack.
But look at this objectively. Ben was one of those incessant childhood readers who regularly won the summer reading program by a factor of ten (except over Danni Cloutier, who was always in that range, which is why we always liked her). His SATV was 800. If people like Ben don’t intuitively pick up what the rule is when they are immersing themselves in literature, then the rule doesn’t exist anymore. It doesn’t matter what the rulebook says is a foul if the refs never call it.
There is a disconnect between the older material he read, which would observe the who/whom distinction, and more modern material where it is disappearing. Disconnect = rule not intuited. In his generation, only those who have been specifically trained to regard the distinction – English teachers being most notable – get it “right” in all circumstances. So it’s not “right” anymore, it is a mere convention used in specialised circumstances, such as public speaking or academic writing. It’s a good thing to learn for those reasons. That’s it.
Whom was already messy and uncomfortable in my mother’s childhood. People were already dropping it out of conversational speech, using “who” for most situations. At the beginning of a sentence especially, “whom” has an unnatural sound. It has not grown more natural over time, certainly. “Who do you want to be?” is not very different in sound from “Who do you want to be with?” though whom is considered more correct in the second sentence. It is hard to know what we mean by “more correct” when a large majority of educated, native speakers don’t use it.
The old rule is “to whom or for whom,” that is, when the object of a preposition. By whom, from whom, under whom, etc. would also be correct. But even to my ear, whom sounds correct only when actually following a preposition – merely being the object of a preposition isn’t enough anymore. Whom are you looking for doesn’t sound right (For whom are you looking now sounds stilted because of the word order).
This is a spot where you can observe language change as it happens. The generation younger than I (another construction that is changing) will get to see it even more clearly. When they are old, whom will exist only in specialised cases. Typically, a usage will remain in a language only in set phrases, long after it has disappeared from standard construction. To whom it may concern, or from whom all blessings flow will persist for quite awhile yet, preserving the form in amber. Because of its association with archaic phrases, whom will seem more and more to be merely an old word. People will use it for humorous effect to suggest excessive formality or age, stuffing it in anywhere without regard to whether it conforms to an actual dative* usage or not. I can’t think of specific examples, but I believe that is already occurring, using whom in much the same way that the –eth conjugation is used on verbs to sound all King James and holy.
Incidentally, although this is the same dative* form as he, him/ she, her they are not changing in the same way. I don’t know what will happen with those, but they bid fair to persist. It illustrates that where the word is placed in the sentence exerts more power in current English than what its actual part of speech is. Favoring word-order over diagrammatic construction is a long trend in English; the sound of certain combinations gradually pushes out the latter over time.
*It’s not a true dative either, but now we are getting into matters ridiculously obscure and unnecessary.