Mobilefags beware!
The official YouTube app will now leak your youtube account/channel in the si parameter of a youtu.be shortlink. This is what gets copied to clipboard when you use the share button under the video. When you send the link to someone and they open it with YouTube app, YouTube will create a chat conversation between you and the person you sent the link to. Yes, YouTube now has an instant messaging service.
To avoid this, always remove the si URL parameter from youtube links, this is the "si=(random string)" stuff after the ? character in the link.