internet - Wikipedia blocked

The free online encyclopedia Wikipedia has been blocked by the Chinese internet nanny. IN the past years this happened a few times to the Chinese edition of the world's largest free encyclopedia, now all edition can in China only be seen by using a proxy.
Tests from both Shanghai and Beijing show the block occurs at the level of the backbone, where the filters are located.
The blogspot-domains, millions of weblogs provided by blogger.com have just been unblocked after three years of blocking. Speculation on why both moves have happened have not yet resulted in a logical explanations. That might not be there.