Voicethread

Voicethread is a technique used on the Internet that allows many different people at many different places the ability to access and communicate together on one web page.
A picture is uploaded and each person wanting to comment on the page inserts a picture of themselves. Once their picture is on the site, they can begin talking. Others on the site can hear the other person speaking and then they may have a turn as well.
Go to http://voicethread.com to see this in action.
I would not use this in my high school class. If it were used for an actual learning purpose, it would be most useful on a college web based course. If I need to play a video, I will just get the video and allow my class to watch it. Discussion would take place afterwards.