Lexicon Valley: Why we keep saying “between you and I.” - Slate Magazine

Do you flinch when someone says “between you and I”? Textbook English tells us it’s ungrammatical, and yet it’s arguably more common than the officially sanctioned “between you and me.” Tennessee Williams, Mark Twain, William Shakespeare—all were guilty of using “I” when the sentence cried out for “me.” Or maybe they weren’t so guilty after all. Bob Garfield and I discuss the oft-uttered, much-maligned “between you and I.”

http://www.slate.com/articles/podcasts/lexicon_valley/2012/02/lexicon_valley_why_we_keep_saying_between_you_and_i_.html