These videos all seem to play through Flash if it's installed. But if I have Flash installed, I also seem to get many more videos playing through it instead of HTML5 which is still actively "opted-in."

In searching for info on the subject I've seen reported that it's also affecting people using Chrome, Chromium, Firefox, Opera, etc.. Basically all browsers for any number of reasons. Like with all other problems with anything Google, there's no way to contact anyone at Google about it and no one from Google ever responds to their own forums or seems to do anything to actively fix the issue.

Same for other problems like Gmail and Calendar no longer working properly in IE8 even though they claim it's a supported browser. This has been going on for some people since 2010 at least.

I really wish Apple hadn't screwed the pooch with their iCloud otherwise I would have already moved all online sync over that way. As it stands there's no way to use native clients in anything but the latest OS, which means my older systems are out of the loop.