Fears of tough action by Beijing following allegation BOC launders money.
This isn't specifically about Bitcoin, but it's a strong indication that China is not going to loosen exchange controls. It's going to tighten them. "Hurun Report's survey of China's richest people, the percentage of super-rich individuals wanting to emigrate, or who had already done so, hit 64 per cent this year, up from 60 per cent last year." The government of China is determined to keep their super-rich from taking their money with them when they leave.
This has mixed implications for Bitcoin. Legal Bitcoin operations in China are less likely, while illegal ones are more likely.