The most likely culprit is YouTube’s pre-emptive content filters, which allow large media companies to upload content they claim to own and automatically block videos that an algorithm decides matches their own. That would make the glitch the second livestream copyright-policing snafu in the span of a few days: On Sunday, a similar algorithm at uStream interrupted the livestream of the Hugo science fiction awards. The award show included clips of copyrighted videos, though the algorithm didn’t know that the clips had been authorized. [Also, in] early August, an official NASA recording of the Mars landing was blocked hours after the successful landing, due to a rogue DMCA complaint by a news network.

A whopping ten companies (or company algorithms) made copyright claims on the convention recording. Tim Cushing fumes:

There's a few of the usual suspects in there, including AP, UMG and Warner, entities not known to be shy about claiming content that isn't theirs.