But, as columnist Ray Zhou pointed out in the China Daily recently, there might be a counterintuitive classist element as well:

Pajama wearers do not venture far from home and since they are mostly downtown dwellers they are actually sending a subliminal message about their social status. As you may have heard, Shanghai people are extremely status conscious and the location of their home is an important element of this. Downtown is seen as desirable. In other words, you don’t catch a suburban (read, lower-status) person in nightgowns on Nanjing Road, the city’s equivalent of New York’s Fifth Avenue. So, wearing pajamas is tantamount to pinning a badge declaring: “I’m a classy and authentic Shanghainese.”

I rather like Zhou’s suggestion of an alternative form of behavioral engineering:

Let the government give pajamas to rural residents in poverty-stricken areas. Television images will instantly put off Shanghainese and they will give up their favorite fashion choice without any prodding.

The article comes complete with a slide show of some of the best examples of Chinglish. My favorite: a sign at the Oriental Pearl Tower in Shanghai that warns visitors that “The ragamuffin,drunken people and psychotics are forbidden to enter the Tower,” goes on to list forbidden articles such as “kitchen  knife,scissors,fruit knife,sword and so on,” and finally reminds visitors not to bring “articles which disturb common sanitation (including the peculiar smell of effluvium)”.

Maybe a sign-proofreading company would be a good business idea…