as per brokendust: "Yt-Videos have (seems like) randomly lagspikes and a huge loading time. In addition to that, if I want to start/stop a video and click on it, Opera needs ~2 secs to notice what I wanted to do. Even the tab close needs a few sec to get his own function. "
And it is the same for embedded videos or directly at YouTube..
When I load the same page in Chrome everything works fine.