Also know that by design, scripts block a Web browser from doing parallel downloads, so browsers have to wait until a script is downloaded from Google before moving on to any others.
HTML5 holds great potential for creating interactive in-browser experiences, but wielding its power typically requires assorted web design skills and a good handle on JavaScript.
The browser experience within Twitter is its weakness at this point, not because of design, but because of the performance lag you may get when opening a link from a tweet.