This is a touchy subject. Phil's got the most correct answer, Ben's got a practical answer, and I have a problem with Peachey's answer. This kind of construction does happen, even though it's not proper, so Phil's correct there. Ben provides the practical advice that language is diverse and choices like this just affect which segment of the population you sound like. And although Peachey's right that you should probably avoid it, I take issue with the "poor education" comment. Although it's informal, I think very few people would assume someone was poorly educated if they said "Why you..." or "You eat yet?" in *informal* settings. Of course, don't write reports or present a speech that way. But if you're with friends or family, it doesn't sound like poor education. Phrases like "ain't" and "He don't" sound even more informal, and *may* come across as poorly educated, but sometimes they're appropriate. I am a well-educated, native English speaker who prides himself on his proper usage of the language compared to those around me, but even I will sometimes use these constructions in casual situations, specifically to sound more casual. Sometimes, using the absolute correct forms comes across as stuffy or clunky, especially in rural areas, like the one I live in. We change our language all the time to the situation we're in, so if you're surrounded by poorly educated people (or, at least, people who *sound* poorly educated), it might be appropriate to match their style. Just remember to use proper language when it's called for, such as in a job interview! Just be aware that language changes depending on your surroundings. Definitely learn the rules. But once you've learned them, don't be afraid to break them... appropriately.