You often want to be able to calculate the eye-space coordinate of a given model-space coordinate. One of the most common reasons is to calculate the distance to a given object from the camera (depth in the scene) so that you can do sorting of the scenegraph.
There's a Toronto event as part of World Plone Day that I'm intending to attend (free registration is available off that link). Interesting to see the Toronto Plone group organizing something like this. They also have regular meetings for those who are aren't able to attend the WPD day-time event.