YouTube cofounder Steve Chen confirmed that YouTube is working on a live streaming product which would put it in competition with lifecasting startups like Ustream.tv and Justin.tv, as well as the "experimental" Yahoo Live service. We asked Justin.tv CEO Michael Seibel and Ustream.tv CEO Brad Hunstable how their companies felt about the move.

Michael Siebel, Justin.tv:

Justin.tv is the biggest live video startup with the most traffic, the most registered users, and the best community. But it wasn't easy to get to the top spot. There are many hard problems to building and scaling a live video site and Yahoo Live is going through those pains currently. I think YouTube will face similar challenges.
Brad Hunstable, Ustream.tv:
YouTube's reported plans to move into live video is important validation for the market and will bring more awareness to the ways live video is changing the way people access media online. Ustream.TV has been singularly focused on live video broadcasting for more than a year now, and has built a large base of regular, compelling broadcasters who use our simple, reliable and robust platform to stream compelling, event-based content to a broad range of audiences across the globe, many of which weren't before privy to such media. Our growth is further evidenced by the traction we have gained through partnerships with leading companies such as Veoh, Digg, Sun Microsystems, the Republican National Convention, Bebo and others; the 200,000 broadcasters and millions of viewers that are now using our site regularly, and the daily growth we continue to experience. We welcome YouTube to this growing market and are glad that even more consumers will have access to great live video content.
"Important validation for the market," by the way, is standard startup-speak for "Thank God, maybe someone will buy us now." Above, Gawker video guy Nick McGlynn shows us a yummy cupcake on Justin.tv.