YouTube's blocking two weeks ago seemed to be related with the 17th Communist Party Congress, the blocking also coincided with Google's launch of two Chinese language YouTube sites, one in Taiwan and one in Hong Kong.
Now YouTube is back in mainland China. The unblock of YouTube has proved that the blocking of China Great FireWall is extremely arbitrary, but why unblock youtube in this time? I think the reason is the 17th National Congress of the Chinese Communist Party had finished.
I tested the Global YouTube, Hong Kong YouTube, Taiwan YouTube, all became available, that's not bad, also I tested my YouTube account, I find my account in the Global YouTube also can be used in Hong Kong YouTube and Taiwan YouTube, that mean the different site of YouTube use an unified account.
Global YouTube Available
HongKong YouTube Available
TaiWan YouTube Available