Any chance that what you are seeing isn't a Flash presentation, but rather an HTML5 Video file being played?

Only if Youtube has switched to HTML5. When I began to suspect Flash wasn't being disabled I checked there and videos still load. It also amuses me that developers have gone to such extreme lengths to make their lives more difficult by coding for a "standard" which hasn't yet been ratified and is therefore not yet a standard.

But that does raise the issue of having the capacity to disable HTML5 silliness in future versions. About fifteen years ago I started doing the majority of my browsing with JavaScript turned off because I didn't want my browser to look (and occasionally sound) like the top of an ambulance, and because mouseover menus cause more problems than they solve. Things are trending that direction again and eventually the only option will be to use a pre-5 browser. Not really looking for a response about this, just something for the devs to consider.