Nothing against builders Sboy, but I did meet a fair few wheeler dealers and crooks in Shenzhen. not just aussies, but brits, kiwis...you name it!

One guy I knew was even into the amateur porn business...in China...go figure.

The problem is it's easy for many who have done the viet/thai route to get a visa in HK and Shenzhen is so nearby with work...just my take.