Today I released an update for the Vanilla 1 extension AutoLinks, to 1.7 from 1.6.
It mainly contains changes to the YouTube embedding code. It improves privacy, enables HTML5 and allows the videos to scale to lower resolutions.

With regards to the privacy improvements, normally when you visit a page that has a YouTube video on it, YouTube (Google) sets cookies to gain what some people consider to be personal information. It’s nothing serious but I don’t think it’s good default behaviour when the person hasn’t even viewed the video.
So if you update to the new AutoLinks, YouTube will not use cookies unless the user actually plays the video.