We are cautioned in grade school to avoid use of the double negative -- that logically, the 2 negatives cancel out, and if that is not the intention of the writer, confusion rules. But multiple negatives do abound, and not merely for emphasis as is "No, no a thousand times no...."
Wolpow, Edward R.
"NO NO NO (NO, NAY, Never....),"
Word Ways: Vol. 44
, Article 26.
Available at: http://digitalcommons.butler.edu/wordways/vol44/iss2/26