FLV runs using Adobe Flash Player, which, according to Adobe, can be viewed by 96.2% of web users who have Flash Player installed.
According to the Library of Congress , FLV is a "binary file format that delivers "bitmapped" video, limited to one video and one audio stream per file, over the Internet to one or another versions of the Macromedia Flash Player. FLV content may also be incorporated in SWF files by ActionScript external references."
There are many sites like this one that use Flash navigation for the website. This particular one hides the menu while the video is playing. Thankfully, my ego isn't crushed too easily, or I would be too embarrassed to tell you that it took me 3 viewings before I even realized there was a menu. The navigation bar pops up when the mouse wanders toward that area. Until it appears, the line across the page simply appears as a progress bar as you view the video.
This type of navigation is innovative, and I think it is a reflection of the newer generation of web users (who, would consider me old, although I don't think I am....yet). Are users of my generation used to having everything you could possibly need to access on a website present and visible at all times, and the newer generation knows that it's there...somewhere, so they'll proactively look for it? Are they so used to living in a generation where professionals with a good sense of usability designed most of the navigation in their site, so the users have confidence that what they need will be there? I'm not sure, but I think that usability wasn't always as important as the technology and as a result, you get some pretty crazy designs.
In this particular website, it makes sense that you'd want a clear screen to be able to view the video, so I agree with the web designer's navigation.