The UFC press release notes that while the sites were originally developed to bring user-generated content to live audiences, many users have instead chosen to use the site to illegally broadcast or upload copyrighted material, including UFC events.
"I can't wait to go after the thieves that are stealing our content," said UFC President Dana White. "This is a fight we will not lose."
The UFC sold over 7 million pay-per-views in 2009, making them the largest pay-per-view provider in the world. That figures translates to around $350 million in gross revenue.
Still, the company believes it's lost countless millions more due to piracy from the streaming sites. In the release announcing the subpoenas, the UFC cites examples, saying that over 36,000 people watched a live feed of UFC 108 from a single IP address. Less than two months later, the same IP address supplied a feed of UFC 110 that was watched by nearly 80,000 people.
The company notes that "Zuffa encourages the development of new technology to deliver UFC content to licensed online platforms, mobile devices, and gaming systems. However, Zuffa does not condone the use of streaming video or other new technologies to violate intellectual property laws, and it will vigorously protect its copyrighted content against piracy in any medium."
Justin.tv and Ustream.tv did not immediately respond to request for comment, though both sites feature copyright policies that offer protection against intellectual property rights infringements.