I care because I like Chrome and was enjoying using it to play H.264 video. I may switch to Safari.

I also care because I was very excited about the near ubiquity a video codec had finally reached in 2010. I don't want to go back to encoding for multiple formats (I hate you 3GP). I won't encode multiple formats until I have to, but the transition to a new standard is always painful and time consuming. If WebM "wins" I get to re-encode thousands of videos and since we now outsource that to Zencoder that means thousands of dollars to do so.