As such, y'all was created. While it is not mainstream, it is very efficient and serves a useful linguistic function.

Let's look at our pronouns:

I (first person singular)
you (second person singular)
he, she, it (third person singular)
we (first person plural)
you (second person plural)
they (third person plural)

One can easily see that we use the same pronoun (you) for second person singular and second person plural. "Y'all" is a colloquialism that creates a distinct, second person plural pronoun, and it eliminates confusion by clearly indicating that it is plural.

There are many things that cause me to be ashamed of my home in the Southern United States, but the word "y'all" is not one of them. It is precise, and it is more efficient than "you all" or "youz guys" as I have heard spoken by some of my Northern friends. "Y'all," in fact, is one of the South's great linguistic achievements. I use it, and I celebrate it (though I admit that I avoid it in all but my most familiar conversations because it is, still, a regional colloquialism).

-Laelth

Edit:Laelth--sloppy proofreading.