On YouTube you can allow comments on your video with timestamp. E.g. a user can watch the video and write:
13:22 great moment!
When you click on the timestamp it will jump to that point in video.
I think this could be a great tool for group discussions or education. However I have some event videos which are about 2 hours long. I'd like to be able to do this privately within my work team. Can anyone recommend any apps (not necessarily web apps) to do this?