It started out, reportedly, with a single word: "HI."
That was early last week. By the weekend, a full-blown Post-it note art war had erupted on Canal Street in New York City, with a number of agencies participating—including Havas Worldwide, Horizon Media, Cake Group, Biolumina and Harrison and Star. (Update: Getty Images has also been involved.)
On social media, the posts have been tagged #canalnotes and #postitwar and have been flooding in. It's a wonder any client work was getting done at these shops last week.