As Google (GOOG) notes, there’s no formal explanation yet for the block, though it may be in response to a seven-minute video posted to YouTube last week showing Chinese soldiers brutally beating Tibetans last March after the riots in Lhasa. China, after all, isn’t renowned for its tolerance of free expression or dissident speech. Remember, animated beat cops patrol the nation’s 13 top portals, warning citizens away from material the ruling Communist Party finds politically or morally threatening.

Asked to comment on the block, Chinese foreign ministry spokesman Qin Gang claimed Beijing was unaware of it. “Many people have a false impression that the Chinese government fears the Internet. In fact it is just the opposite,” he told reporters. “China’s Internet is open enough, but also needs to be regulated by law in order to prevent the spread of harmful information and for national security.”

In a 352-page report published last week, the National Research Council said data mining and behavior detection aren’t nearly as useful as their proponents claim. In fact, they’re of dubious scientific merit and have “enormous potential” for infringing on law-abiding Americans’ privacy. “Automated identification of terrorists through data mining (or any other  known methodology) is neither feasible as an objective nor desirable as a goal of technology development efforts,” the Council found. “Even in well-managed programs, such tools are likely to return significant rates of false positives, especially if the tools are highly automated.”

While not an explicit condemnation of the techniques at issue here, the report does recommend that the government evaluate the effectiveness and lawfulness of these data mining and behavior-detection programs it’s so keen on before implementing them, and periodically thereafter. Said the Council, “History demonstrates that measures taken in the name of improving national security, especially in response to new threats or crises, have often proven to be both ineffective and offensive to the nation’s values and traditions of liberty and justice.”