You're probably wondering why you should review the database structure one last time, given that you've paid attention to every detail and have focused on data integrity throughout the entire design process. The answer is simple: You want to make certain that the data integrity you've been so careful to establish is absolutely as sound as possible. As you well know, a crack in the integrity could result in inconsistent data or inaccurate information. However improbable, it is possible that you may have overlooked something. The peace of mind you gain from knowing that you have a solidly designed database is well worth the time and effort of this final review.
Remember: Garbage in, garbage out!