[jerryzh]

There is actually a Chinese solution to this which you wouldn't prefer at all. Legally every place who provide free wifi will need you to do sms verification with your smartphone, and record your ip with your smartphone number (which in China is connected to your identity). Then they need not worry about liability, because if anything goes wrong, they can tell the police exactly who you are.

If you want both privacy and liability, it seems indeed only you can do is to be harsh on larger entities like cafe shops who provide free wifi.