Eben made many corrections, in students' papers, involving number-agreement. For example, "Why does everyone ignore their passions?," as opposed to, say, "Why does everyone ignore (his) / (her) / (his or her) passions?"

I was curious what Eben and others had to say about this construction. Unlike a mere typo, this construction comes out in people's papers because it's common in colloquial speech. But more than that, I would say that it has now achieved a status of sounding correct to native American English ears. And I would even go so far as to say that it is close to having achieved a "correct" status in written English prose, if it is not there already. Eben clearly disagrees with this proposition. My questions are:

1) Is the construction "wrong" in formal writing?

2) If it is "wrong," is it close (say, a decade or two away) from being right, as a result of natural evolutionary tendencies in language?

3) As lawyers, or even as professionals in general, are we well-advised to write conservatively, with traditional rules of grammar ("up with which I will not put"), or will it be considered sloppy (and make us seem illiterate, as Eben says) to push some of these rules toward what seems to be their natural dissolution, in our own writing?