If you aren't already aware, there is an interesting legal battle going on at Wrigley Field. The Cubs ownership wants to install a video board, but this board would block the view from the neighboring rooftops. The interesting economic question to me involves both externalities. As it is right now, the Cubs generate a positive externality in the form of games being viewable from neighboring rooftops. Putting a large video board along the outfield wall would block this view to some extent.