Bear in mind that the Flash Player will play VP6 (native flv) and recently H264 streams. Adobe already licensed both codecs for use in their free player.
If Google were to open source VP6 (as well as or instead of VP8) then suddenly all the Flash video files that everyone's created already to play with Flash Player will work in upcoming HTML5 video implementations, giving everyone one format to rule them all (it's about equivalent in quality and cpu usage to h264), playable both in legacy browsers with a Flash player or in fancy new browsers with an HTML5 video tag.
Problem solved.
Now, come on Google...