I was in Guangzhou for two weeks recently with friends. While walking to a restaurant downtown, three cops stopped us and asked to see our passports. We didn't have them. So, we were escorted to the nearest police station where we were told to wait in an investigation room. A few other foreigners in the same predicament were also there. We had to phone around and get our passport numbers to write down, as we were told we could be deported otherwise. Then we had to pay a fine for not carrying our passports (I literally saw the cop put my money in his pocket). Anyway, just thought that people should be aware of this inefficient and blatant money-making scheme.