Ustream is being used by our organization to stream and broadcast live events and missions of NASA's Jet Propulsion Laboratory. Broadcasts can be archived and viewers logged for historic data.This gives the organization visibility into the type of material that is popular and trending amongst peers, as well as the public.
The employee community gains insight on current missions, accomplishments, and future goals by seeing visually what is happening with their own eyes. For those who work behind the scenes to make JPL's mission possible, they may not always see what their hard work and dedication help to achieve. Live streams are a way to witness such events.
It's hard to compete against YouTube as it's a household name. While Ustream may not have been around for a long time, it's gain in popularity in such a short span is a testament to it's service and features. JPL must have been impressed with the product to choose Ustream for their video content delivery.
With other popular video streaming services such as YouTube, it can be quite a challenge to compete against. For enterprise use though, I find Ustream to be adequate and easy to use for the user community.