The Google Talk Labs Edition will launch a YouTube video in the chat conversation based on a link someone chats to you so that it continues to run while you continue to chat. This is, of course, not any kind of universal standards-based solution but for me it illustrated the value of being able to view a video without it dominating the context in which it's being viewed.
It seems to me the answer here is for HTML 5's video element to gain traction. Then we can get the codec and interface out of the walled garden of whatever Flash video player sites have crafted, and put the control back in the browser. If Safari wants to offer the option to pop-out a player window, it can.
