<i>Even in the case of video, where Flash is enabling over 75% of video on the Web today, the coming HTML video implementations cannot agree on a common format across browsers, so users and content creators would be thrown back to the dark ages of video on the Web with incompatibility issues.</i><p>Not really. Most of that 75% is in h.264, a format supported natively by every browser/platform that doesn't support Flash (e.g. iPad) and some that do (e.g. Chrome). Even Microsoft, if and when they do implement &#60;video&#62;, are likely to support it.<p>It may be messier than just assuming Flash is available (welcome to web "standards"!), but I would hardly call it "the dark ages".