This is great news for open source enthusiasts. Several of us have long been fans of the Ogg Vorbis codec. Seeing a similar codec for video is certainly a boon for free software in general.
In addition, as HTML5 introduces support for a <video> element. Embedding video into browsers with Theora support, such as upcoming Firefox release, will be as simple as:
<video> <source type="video/ogg" src="mymovie.ogg" /> </video>
While there are several other video standards with a much broader install base -- most notably Flash, Windows Media, and Quicktime -- all of them have some sort of licensing penalty that make them non-free-as-in-beer. Time will tell if Theora is destined to be the next true video standard or remain a niche format.