Google is trialling video with autoplay on its search results. These videos will not only appear automatically, but will also play their audio automatically. It's this that generally causes the greatest consternation among users who don't want to jump out of their skin because some video starts chatting away.
The natural conclusion from this trial is that Google might eventually decide to use autoplay on video ads. Although there's no evidence that this is currently happening. Google is, at heart, an advertising company. It made $22.67 billion in the three months to June 30th, which is 87% of all the money it makes.
Google is only trying this on for size, SEM reports that Google confirmed the test but went on to say: “We are constantly experimenting with ways to improve the Search experience for our users, but have no plans to announce at this time”.
If you hate autoplaying video ads then there are some blockers available for Chrome and Firefox that will stop them from playing, but not prevent them from appearing. This gives you the chance to press play if you're interested in the advert. Look for "disable HTML5 autoplay" in the relevant places for your browser. [SEM via Ubergizmo]