A great point about the way languages changes—and how fickle people are about that—from John McWhorter in Books & Culture (Jan/Feb ’09):
Every word in a language is the end product of eons of heedless transformation. The lay public is mesmerized by this process and endlessly curious about it (so long as the explication doesn’t become too technical) and yet tends to view current manifestations of the same kinds of change as lackadaisical and repellent. If ēt picked up a stray g in early Old English [and later became our word “yet”] it’s just how language changes, but if today other picks up an n (in whole nother, modeled on another), then the time to repent is at hand.
In other words, usage determines meaning, spelling, even whether or not a word is colloquial or standard. No one has the authority to say that nother is not a word or that they cannot be singular. If enough people say it, it’s right. It’s the new standard.