Correct = whom
As several people have observed, the correct form is *whom*. It is, in fact, the object of the preposition *of*, which happens to come at the end of the clause. That construction is all right, even in formal writing (though it can be even more formal).
Now, if you are presenting the dialogue of a character, you will always want to use the language that the character would use. Most people, in ordinary speech, would use *who* in the example (though it sounds awful to me!). But in any kind of expository writing, as in an article on some sociological topic, you would want to use the correct form. At least, you should ... but I see all kinds of abominable uses even in formal writing these days. This happens mainly, I think, because people no longer learn correct English in American schools.
*Whom* may be fading, but only because the United States is now a nation of poorly educated people who just do not care about anything except buying the latest electronic gadget that lets them send messages like "what r u doin" and "c u soon" and so forth. Heaven forbid that anyone might actually study grammar and rhetoric and the history of the English language and try to master its nuances.
For the record, *who* and *whom* are almost always used wrong in the media in the US in any kind of semi-complex situation. Usually when the idiots on TV try to get it right, they will use *whom* when, in fact, it should have been *who*. For example, they might try something like this:
*The ticket will go to whomever gets here first.*
They think about the word *to* being a preposition, and they have some vague memory of objects of prepositions, and they decide it must be *whomever* because it is an object. However, the entire clause *whoever gets here first* is the object, not the pronoun alone. It has to be *who(ever)* because that is the form for a subject. *Whoever* is the subject of *gets* in the clause.
Hey, if you think the rant was bad, you ought to see the stuff that I cut out!
