"Victimless" crime, such as DVD piracy and prostitution is rampant. For the former, just walk down the street and you'll either see a man with a ratty-looking suitcase or a shop full of DVDs. For the latter, just look for any barber's shop with pretty girls and pink neon. Some marijuana dealing does happen, though it's rare for most Chinese to hear about it. It'll usually be through a Xinjiangnese discreetly (or not so discreetly) muttering "hashish" to you. Being a law-abiding and god-fearing citizen I don't really know much about it, except that it's got quite kick to it. Taking drugs is very illegal of course, but the police generally turn a blind eye to foreigners and their peccadilloes, as long as it's not too public and Chinese aren't involved.
Really, the only common "crime" here is dangerous driving -- there are only two kinds of pedestrians, the quick and the dead. Try to stick to the former, since tire marks generally don't look too snazzy.
All in all, it's probably the safest city, large or small, that I've lived in, and nobody, at least not the expats, really worries about crime at all.