It's not grammatical English, but nor are a variety of other constructs that we see as normal, such as "ain't no," or even "they" as a gender-neutral singular pronoun (this one matters only to sticklers). Convenience need not obey the rules. Would love to expand further if you are interested.

Also: http://www.amazon.com/Eats-Shoots-Leaves-Tolerance-Punctuati...