MileyCyrus appears to know more than me about the legal ins and outs. I have heard the required insurance referred to as bodybag insurance but at the same time I've friends who woke up in a hospital after an epilectic fit who just left. No one chased them for any money. I imagine if you go bankrupt you scrape together the money to go home and do so unless you've pissed off a powerful person enormously. I know of people who are in their third stay in prison for running gambling dens so whatever else they do they don't deport people for comparitively petty shit like going bankrupt. Or they might, if you declare it on the form applying for a new visa.

On a similar note, if the border guard or visa desk guy asks if you are working on a tourist or student visa the answer is no.

As far as violent crime goes I'd be surprised if Shanghai was as violent as New York or London. Gotta watch your wallet/purse/bag though. There are professionals all over.