It's not a shocking news, however. Apple has already moved [1] some of its storage servers to Beijing. The attack could just be the authorities making sure that Chinese users' iCloud data is actually stored in China.
[1] http://techcrunch.com/2014/08/15/apple-taps-china-telecom-as...
I realize this isn't the real reason why China told Apple to build a datacenter there, but that's the one they used publicly, and as long as the company itself can get access to that data, then the argument is a pretty plausible one, even from China. Apple, Google and others could weaken this argument by adopting end-to-end encryption for their services.
Unfortunately, it seems the companies decided to keep the data as is, but build the data centers in Russia, China and wherever else they might ask them to do it.
Ultimately there's only so far you can go against the wishes of the Chinese government when your factories are there, or against the US government when your HQ is there.
http://www.reuters.com/article/2014/08/06/us-china-apple-idU...