My employer (smartly) prohibits bringing any corporate equipment into China - including cell phones which access company email, and generally suggest not touching the Internet (at least any of your accounts) at all.
Having been there, this is honestly very good advice.
I heard Google does that. I work for Microsoft and am based in China, so obviously this is not an option for me. It turns out not to be a problem in practice, everything is encrypted well enough, the only annoying thing are GFW-instigated DOS attacks on secure connections.
Having been there, this is honestly very good advice.