It's really not an ideal solution. Does F11 even work on the Mac? I F11 in Chrome, I get no (ahem) chrome, but if I F11 in Firefox and IE, my tabs are still there.
(EDIT: just realised they disappear after a little while. Interesting.)
In any case, the fact that there is nothing clickable is baffling. I really don't understand why no-one thought to tackle this when discussing the <video> tag.
I love this behavior actually. Besides the fact that Flash has had years to get fullscreen right, I've yet to have it worked 100% as expected and I might as well light myself on fire as try to use it in Linux.
(With HTML5 <video>) I can easily get the video to go fullscreen in the window (as is the behavior of "fullscreening" video in Chrome) which is nice because I can have a video play and not have to have my browser window at the normal size... and if I want, I can press F11 and have it go full screen (without borking my computer in the process). (Who cares what the button is... is the clipboard going to fail because it's Cmd+C in OS X and Ctrl+C in Windows?)