I'm all up in the agreementactity with Umbran as far as it being both group concensus and actual rules... but I loathe that particular rule. Other people have mentioned the not-real nature of the rule, given that it was more or less invented when everyone decided to make English a romance language with no regard for actual history. What really gets me, though, is the fact that it puts such an artificial barrier between common vernacular and "proper English". If you walk into a room in the middle of a conversation, do you ask, "About what are you talking?" No. Do you go with, "What are you discussing?" Probably not, unless you care deeply about the rule. The vast majority of us simply ask, "What are you talking about?"
And I come at this from a rules-lawyer perspective where writing is concerned. I will get all over comma splices and misplaced modifiers and diction issues, because those might actually result in difficulty understanding the meaning of the sentence. But the person who says "bad grammar is something up with which I will not put" has made him-or-herself more difficult to understand in the pursuit of false grammatical perfection.
And I come at this from a rules-lawyer perspective where writing is concerned. I will get all over comma splices and misplaced modifiers and diction issues, because those might actually result in difficulty understanding the meaning of the sentence. But the person who says "bad grammar is something up with which I will not put" has made him-or-herself more difficult to understand in the pursuit of false grammatical perfection.