I was there watching live, so I didn’t know anything about this until after the fact, but Io9 describes what happened:
How copyright enforcement robots killed the Hugo Awards [UPDATED]
Last night, robots shut down the live broadcast of one of science fiction’s most prestigious award ceremonies. No, you’re not reading a science fiction story. In the middle of the annual Hugo Awards event at Worldcon, which thousands of people tuned into via video streaming service Ustream, the feed cut off — just as Neil Gaiman was giving an acceptance speech for his Doctor Who script, “The Doctor’s Wife.” Where Gaiman’s face had been were the words, “Worldcon banned due to copyright infringement.” What the hell?
You can read the rest of the story here.