Possible Solution: Annotations are working properly in Chromium:
sudo apt-get install chromium-browser
More info about the problem:
Today I noticed I have this same problem. The annotations on my videos and on other user's videos were visible, now they are all gone. I want to add a few details that might help:
- When I edit the annotations on my videos they are correctly shown in the annotations editor, but not when watching the video normally.
- I use adblock plus, but disabling it completely does not help.
- The new annotation ads that youtube includes in the bottom left corner of some videos are visible (the ones that slide).
- The channel icon people can add in their videos in a corner is visible.
- Ads in general are visible.
- When I right click in a video it shows me, among other things, "About Adobe Flash Player [version here]". So I am pretty sure it is not the html5 player.
As stated above, the annotations are working properly on Chromium.