In ArcGIS 10 users are able to link the extent of one data frame to the extent of another data frame and optionally zoom to features that intersect the other data frame's extent. Another option should be added so the user can zoom to features that intersect the center of the other data frame. This would be handy for maps with a point of interest/focus (e.g. an address location) in the center which plots close to the edge of the index feature (e.g. county boundaries) but the user only wants the inset map zoomed to a single index feature.