At theatlantic.com, Megan Garber has learned that whom is on the way out.
All right, folks, show's over. Nothing to see here. Move on.
Or, in the event that for you, as for Megan Garber, this is big news, I can refer you to the Oxford English Dictionary, which has noted for some time that whom is "no longer current in natural colloquial speech." Or my own post on the subject from two years ago.*
Apparently Those Damn Kids and their confounded texting have something to do with it. Ms. Garber writes, "Technology seems to be speeding the demise. Online, on-screen, strict rules are systematically broken—for brevity’s sake, for clarity’s sake, and sometimes for the sake of ease or irony or fun. (Because LOL, amirite?!)" Cute.
Unfortunately for her argument, to the extent that it is an argument, she wrote four paragraphs previously: "According to Google’s expansive collection of digitized books, the word has been on a steady decline since 1826. The 400-million-word Corpus of Historical American English records a similar slump. Articles in Time magazine included 3,352 instances of whom in the 1930s, 1,492 in the 1990s, and 902 in the 2000s."
So evidently the decline began with Those Damn Kids during the John Quincy Adams administration.
And, of course, we increasingly value casualness and informality in both conversation and writing. Full Marks to Ms. Garber for spotting a trend that has been going on for a century in American English.
You know from simply listening to people that whom has largely vanished from ordinary daily conversation. The corpus information shows how sharply the usage has declined in published writing. And I have my own anecdotal evidence that the pronoun is on the skids.
As the de facto go-to grammar guy in the newsroom, I get the question once every week or two: "Should this be who or whom?" The question comes from educated adults, professional writers and editors, and it almost always comes in the same syntactical context.
Whom survives mainly as the object of a preposition, as Geoffrey Pullum has explained, but consider this specimen sentence: They will vote for whoever they think will win the primary. The impulse is to see whoever following the preposition and assuming that it ought to be the object. But the whole clause, whoever will win the primary, is the object of for, and whoever is its subject. This is almost invariably the kind of sentence that is brought to me.
If educated adult writing professionals have to stop and diagram a sentence in their heads before deciding whether a pronoun is a subject or object in a straightforward sentence, then there is probably not much hope of pounding the distinction into the head of the populace.
So, unless you are writing a thesis or are employed by a gauleiter of the peeververein, just use who. The future is with you.
*It could be just vanity, but I think that if theatlantic.com had used a comma in "For whom the bell tolls" in the headline, as I did in 2010, it would have been a better headline.