They just need to add the file format to the supported extension list. I'd look in an upcoming build. Since they work, I'm sure they'll add it soon.
PS. Matt, if you are going to have people test this, OGV is probably a better extension to use. WebM is really OGV videos with a specific set of codecs supported, I think. They're ugly codecs, but whatever...
There's nothing that fancy about WebM. I can't imagine there would be any part of them that Red October wouldn't already handle. I'd just add the extension to the support list.
