Wikipedia and Firefox support may ramp things up

Wikipedia requires free codecs, so Theora is what you're supposed to supply videos in (and Vorbis for audio). Wikipedia is one of the world's most popular sites. The new version of Firefox will include Theora support - and since that's a browser with millions of users, soon there will be lots of people who will be able to easily view Theora (and Vorbis).

I think that's a dynamic combination. Codecs are a chicken and egg problem - you need to get lots of readers AND lots of content for a codec to succeed. Wikipedia can provide content, Firefox can provide readers.... leading to a great potential for success.