|Who's on First, indeed!|
There is the added irritation that, logically, you can't even lash out at the perpetrator of incorrect usage, because it simply isn't his or her fault. Chances are very good that he or she was taught it incorrectly, or else not really taught it at all.
The word in question: "whom."
How many times, while you were growing up, did you use the word "who" only to be curtly corrected with "whom?" And of those times, how often was it really explained to you? The problem is, as children we were made aware of the word's existence, but never taught how to correctly apply it.
It's like the sea gull in Disney's "The Little Mermaid," WHO is aware of the existence of a fork (or, TO WHOM the existence of a fork is known), but, left to make his own assumptions, decides it is a hair care product.
The result of this semi-education seems to be that many intelligent people -- very many of WHOM are otherwise excellent writers and speakers -- wind up throwing "whom" around with nary a thought as to whether or not it actually belongs. Usually, it doesn't.
So, for those underserved by their teachers, I have a very brief primer on the usage of "who" versus "whom."
Remember: Who did what to whom.
WHO failed in teaching us the proper use of "whom?" Educators.
They failed WHOM? All of us.
Who is ACTIVE
Whom is PASSIVE
If it comes after a preposition (in, to, by, at, etc...), the word is "whom."
If it comes before a verb or verb phrase (including forms of the word "is"), the word is "who."
Who is it? To whom am I speaking?
Grammar Girl puts it this way:
...you use whom when you are referring to the object of a sentence. Use who when you are referring to the subject of a sentence.
I highly recommend reading her whole piece as well, as she dives a bit deeper than I into the subject.
Please, for the love of all that is good and holy, pass this on to your friends. Heck, copy it and paste it in an email. I don't care. But if I keep seeing people using "whom" incorrectly on facebook, I'm gonna snap.