I'll pinch in here; webm is fairly new, and meanwhile the technology itself is great the issue comes that our forums without some recoding wouldn't support this. What this means is that we would have to recode some deep parts of the software to support webms, but it's not a task that's impossible. (My brief search didn't result in any mod that would make it easier as a task)

From the UX, and overall design standpoint I don't think the task implies any difficulty or insecure grounds.