This logo is an iconic piece of postmodern design because it plays upon the cultural knowledge that the symbol of the 'heart' is a semiotic signifier of 'love'.
This new logo achieved something that has never been done before, it used graphic design to successfully "rebrand" a city's image. The rebus has become iconic and reproduced in various ways countless times; on mugs, t-shirts (often worn as a fashion statement by people who may have never been to New York).
The logo has been redesigned and altered over the decades;
It has also been used by other cities all over the world, replacing 'NY' with any other city name or country name as a tourist souvenir.
Last year the logo was re-imagined by BBDO in a new campaign to improve New York's global image. This new campaign involved public participation asking people to alter to logo by replacing the 'heart' symbol in the logo with another object that they believe to represent New York in some way.
David Lubar of ad agency BBDO said the old logo had been “co-opted by literally the rest of the world. If you go to Russia, if you go to Spain, you see ‘I heart something’ and it’s lost its New York cachet. My team’s assignment was to bring new cachet back to that logo and make it mean something important.” (http://www.telegraph.co.uk/news/worldnews/northamerica/usa/9303192/I-Love-NY-logo-set-for-makeover.html)
BBDO's re-imagining of the iconic logo is a pastiche and opens it up to a personal interpretation from the audience rather than a cultural interpretation. This is an intrinsic part of postmodernism because it allows the public to pastiche the logo with the own personal response to why they 'love' New York.
Milton Glaser responded with "I saw one that said ‘I Pizza NY’. I don’t get it.”