<i>Safari hasn’t chosen it as the default, it’s chosen it as the solitary option.</i><p>Not true. They've chosen to implement it in a codec-agnostic way. It simply requires installing XiphQT, which itself only involves moving a file into a folder. This is unlike (say) Mozilla, to which &#60;video&#62; support of h.264 cannot be added by any means.<p>You could argue that Apple have made it the solitary option on their mobile devices, but that's because it depends on the availability of hardware decoder support, which doesn't exist for Theora.<p><i>and the argument would be moot.</i><p>No, the argument would shift over to trying to get content creators to use Theora, even though 70% or so of the browsing audience doesn't support it or &#60;video&#62;. Web video would still be dominated by h.264 in Flash, the only format that would work everywhere.