When a user is being shadowed, they should be able to disconnect their shadowers when...
* they are satisfied with the help they have gotten
* they can no longer monitor what the shadower is doing to their session
* when they want to do something that the shadower can't see
and so on.
With the current state of things where the user has no input on whether they want to be shadowed or not, the shadower could just initiate another shadowing session, easily circumventing this mechanism.
If we would consider bug 37, where we would offer the user a choice of being shadowed, this feature starts to make more sense - if the user accepts to being shadowed, we should also allow the user to change their mind and throw out any shadowers.