"The double negative works in a similar way to strenghens an idea - as in "ain't no use." The double negative was once widely used in everyday speech to emphasise a negative. It was discredited and done away with by formal grammarians some time around the nineteenth century so as to make language conform to the formal rules of mathematics where a double negative equals a positive."

English differs from some other languages in eschewing double negatives. In French, they're common, for instance. But even in English - regardless of how it came about - "ain't" sort of calls for the double negative.   I do accept "ain't" as more of a colloquialism or slang than "bad grammar," and how often does anyone say "I ain't got any cigarettes?" or "I ain't had any loving (as opposed to 'lovin'") since January, February, ... ?" You don't usually speak or write proper, standard English but then throw in the word "ain't."   But it's not at all uncommon for someone to speak or write something with perfect, standard grammar except for saying something like "between you and I."

Joe, I generally agree with this: "I think that if a grammatically-incorrect language construction appears commonly in spoken English, it's perfectly OK to use it in a lyric. But when it's not common usage and done just to match a meter or rhyme, it's WRONG, WRONG WRONG!!!! "

I guess the question is, how "common" does something have to be before it becomes "acceptable?"   I'll admit that there are instances where the pronoun "I" SOUNDS awkward and weird to me, even though I know it's "correct." E.g., "That would be I," sounds odd, while "It is I" does not," to me - but "It's me" also sounds OK. Maybe it's just a matter of familiarity, and eventually "Give it to him and I" will (shudder) also sound natural. But so far, even though that kind of construction has begun to be used more and more in the last decade or so by people who should know better (English majors, newscasters, teachers, etc.), it hasn't become "standard usage" by well-educated, articulate people. That's why I hate its usage in song lyrics.

I also think that when poor grammar is used in the lyrics of commonly heard songs it tends to make people THINK it's correct.   Not so much with colloquialisms or slang, but when an otherwise grammatically correct lyric includes one incorrect usage such as "for you and I."   

I know that sometimes it's done for the sake of rhyme. An old trad song, has the line "For poor, ornery people like you and like I" to rhyme with "I wonder as I wander out under the sky."   But Iz (Israel Kamakawiwo'ole) has a fairly popular song, with lyrics in Hawai'an and English, that has a tag line "for you and I," which isn't part of any couplet or rhyme scheme. Totally unnecessary to use "I" instead of "me."   And today's music lyrics often don't rhyme anyway.   I've known of songwriters who often dispense with trying to rhyme yet will use "I" instead of the correct "me" apparently just because it rhymes with a previous lyric word.