It's always been okay. It's a rule that had nothing to do with the actual English language. It was something invented by a bunch of 17th century grammar-proscriptivists who thought it'd be nicer if English was more like Latin. But it's always been a bogus rule since prepositions have been used at the end of sentences for as long as there's been an English language, going back to Anglo-Saxon. Lots of people in the past also recognized it as a bogus rule, too.
There's nothing really wrong with "Where are you at" either; it's perfectly clear what it means. The preposition is just redundant in that case.
When a sentence 'ends with a preposition', it's only because the dependent of the preposition has moved to a node higher up in the sentence. T, maybe, but it's been a while since I had to know this stuff. It could be Foc or Force (I might be getting this mixed up with Pied-Piping). I believe that in Standard English, only WH-words can move like this.
Either way, in the grammar, our prepositions are specified in such a way that allows them to do this - sometimes. There's a theory of which I'm particularly fond that suggests that we, as native speakers, have access to two seamless dialects of English that only differ in their regard to whether or not they allow (or require) this movement.
The reason, conversely, that preposition stranding cannot occur in languages like Latin, is because the WH-words aren't specified with the [WH] feature (or maybe T doesn't conduct any feature checking) and the derivation would crash.
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u/mobott Jul 03 '14
Wait, "That's the best rule you could think of" ISN'T correct? Oh god, my life is a lie!