For the most part, areas known for prostitution, drug trafficking, as well as “bar streets” and particularly night clubs seem to be the primary focus of these ID checks. In some cases, among those who cannot produce their passport, an apologetic and courteous demeanor often seems to favorably resolve the matter and, barring that, a prompt call to one’s foreign affairs officer may also suffice. However, in several cases, the foreign teacher was detained until such time that someone else could fetch and then produce his passport. In another reported case, a fine of 500 yuan was initially imposed but then was successfully negotiated down to 100 after a Chinese friend with some influence was called.
If you are living in Guangzhou, Beijing, or Shanghai and are stopped by the police and asked to produce your passport, do not become argumentative: that will only escalate the situation. Instead, apologize for not having it on your person and explain where you currently work. The worst case scenario seems to be that you will either be detained until such time that someone can bring the passport to you or you may be allowed to return the following day to the PSB to produce it then.
Obviously, if you are living and teaching illegally in any of these three aforementioned international cities, you will probably want to avoid frequenting night clubs as well as areas known for prostitution, drug trafficking, and other crime, especially during the evening hours.