With the release of "QFE3" (Quick-Fix Engineering) version of Windows Live Essentials Wave 3 build 14.0.8117.416, there had been numerous complains about the removal of one-way "show my webcam" feature in Messenger. Piero Sierra of Microsoft explained the changes on official post:
It's still absolutely possible to "share your video" with who doesn't have a video camera. Or see someone's cam when you don't have one….and chatting with a friend who does. In chat window, click "Video" (or webcam icon next to friend's user tile) to set up one-way video call. To mute/unmute audio click microphone. You can control friend's audio by clicking speaker icon. The inverse to this's also supported.
"In past, we offered two choices: either click "Video Call," a full-featured option that includes two-way video and audio. Or "Show my webcam," a one-way feature, where you could show your webcam's video to your friend, without audio."
In latest update, we've simplified the command to "Start Video Call"…There're only really two aspects that're different: It's no longer easy to hide your webcam's feed if you've one enabled when you start a video call (you can still do this using AV settings dialog); You can no longer set up "webcam rings" with multiple people sharing silent video one-way.