Stickies on a Virtual Wall

Just the other day I was at an in-service where the presenter suggested one technique where students could write one question on a wall and others could answer it.  Then he said that during a test students could look at the wall for a minute or so.  Obviously the point was that kids who are less reticent to ask a question would feel more inclined to do so.  Well, while Wallwisher has been around for a few years, it allows students to put stickies on a wall and others can edit (i.e. answer it).  So in the case of my kids who often take e-tests, this would be one way to get a lifeline.