Here’s Google on the matter:
Bottom line, we are at an impasse in the evolution of HTML video. Having no baseline codec in the HTML specification is far from ideal. This is why we joining others in the community to invest in WebM and encouraging every browser vendor to adopt it for the emerging HTML video platform (the WebM Project team will soon release plugins that enable WebM support in Safari and IE9).
In other words, they’re going to try to get Safari and IE users hooked on WebM by working around Apple and Microsoft. It’s an attempt to create a standard by way of plugin. Again, ugh.
And while somewhat interesting, it’s unlikely to work. And it’s a dangerous move away from working together on standards and instead is likely to piss off Apple and Microsoft.
Generally, plugins suck because they’re not standards. Even ubiquitous ones like Flash aren’t everywhere. And that creates headaches for web developers and surfers alike. There will never be a truly unified web with plugins. Even plugins backed by Google.

Authors: MG Siegler