There is quite a discussion happening about Wallwisher in the Technology Bootcamp group called The specified item was not found.
I have used Wallwisher as a "parking lot" in professional development trainings. It is a great opportunity to brainstorm, post and share ideas with a large number of participants. Corkboard.Me is similar tool that I find has fewer bugs and problems.
I use WallWisher to log help requests. I ask teachers to create a sticky note with their room, computer #, and issue. I keep the page up all day and can see as the requests come in. When I address an issue, I delete the stick note!
The only issue I've had is that is runs slow. I think our network was worked on this summer, so hopefully that will be improved.