Yahoo messenger has releases another plugin ( Zyng Video Sharing ) which allows you to watch, share video with chat friends in Real time sync i.e. What you watch is what your friends watch. This is another great extension worth trying and is similar to photo share on Yahoo messenger. It supports Yahoo! Video, Flickr, and YouTube.
All you need is to install this plugin and then invoke it with any friend of yours ( Actions > Choose a plugin ). Once the invitation is accepted by your friend the whole magic starts. This feature can also get invoked if you send a Video URL link of any of the service, the same thing happens when I send a image link which starts image preview.
I tried with Manav and things came out pretty much smooth. To watch it in sync with your friend hit the Watch With Me player. Once done you and your friend will watch it real time together and also can have discussion.
This is useful when you want to discuss on any video or just enjoy it together. Both sides have control over playing the video and you can go full screen. Everytime you play or pause the video the message is sent to the other user.
Find more details on the offical announcement