In this post, Jeremy Likness explains what you need to do in order to understand that a user has scrolled to the bottom of a ScrollViewer.
Recently I came across the requirement to react to the fact that a user had scrolled a view to the bottom. It sounded easy at first because I imagined hooking into a scroll viewer changed event, listening to the event args, and then reacting when it was done. The only problem was that I couldn't find the appropriate event to bind to!